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Cards (634)
Section 1
(50 cards)
public
The name of the class and the file name must match when the class is declared _______
-cp
// to compile javac ___ <classesPaths> -d <compilerOutputPath> <pathToSource>.java
=
The assignment operator is ___
long
____ numbers have 64 bits
float
Double numbers provide double the precision of a ______
classesPaths
// to compile javac -cp <_______> -d <compilerOutputPath> <pathToSource>.java
+
The unary operator that indicates a positive number
.jar
The classpath can include a .zip or _____ file
import
The ______ keyword defines other classes or groups of classes that you are using in your class
String
public class Simple { public static void main(____ args[]) }
L
Append an uppercase or lowercase _____ to specify a long number
.java
A Java class is described in a text file with a ______ extension
byte
______ range is -128 to +127 -- 8 bits
classpath
The default value of the _______ is the current working directory
package
Classes in the .zip or .jar files in the class path must be zipped with the path names that are derived from the directories formed by their _______ names
static
public class Simple { public ______ void main(String args[]) }
braces
Code blocks are defined in ________
class
The ______ keyword precedes the name of a class
main
public class Simple { public static void ____(String args[]) }
compilerOutputPath
// to compile java ___ <classesPaths> -d <_________> <pathToSource>.java
-cp
//to run app java ___ <classesPaths> <packageName>.<className>
command
_____-line arguments are passed to the program through the args[] array
declarations
Method _______ are enclosed in code blocks
methods
Functions that can be performed on an object
*
Multiplication operator
class
Java fields and methods have ______ scope
block
Every class declaration is enclosed in a code ______
java
//to run app ____ -cp <classesPaths> <packageName>.<className>
CLASSPATH
The _____ variable is used by both the Java compiler and the Java interpreter at runtime
args[]
public class Simple { public static void main(String _____) }
underscore
Any number of ______ characters can appear between digits in a numeric field
+
The additive operator and string concatenation operator
main
To run a Java program, you must define a _____ method
root
The directory containing the ____ name of the package tree must be added to the class path
%
Remainder operator
.java
// to compile java ___ <classesPaths> -d <compilerOutputPath> <pathToSource>______
F
Append an uppercase or lowercase _____ to specify a float number
final
The keyword ____ is used to declare a variable whose value may only be assigned once
javac
To compile a Java source file, use the Java compiler called _______
pathToSource
// to compile java -cp <classesPaths> -d <compilerOutputPath> <_________>.java
directory
The classpath can include a list of _______ names
constructors
Functions called during the creation of an object
/
Division operator
modifier
The keyword public in front of the class keyword is a ______ and not required
short
_____ range is -32,768 to +32,767 -- 16 bits
int
_____ rang is -2,147,483,648 to +2,147,483,647 -- 32 bits
-d
// to compile java -cp <classesPaths> __ <compilerOutputPath> <pathToSource>.java
void
public class Simple { public static ____ main(String args[]) }
-
The unary operator that indicates a expression negation
instance
Variables, or the data associated with programs are called ________ fields
Section 2
(50 cards)
private
One way to hide implementation details is to declare all of the fields _______
for
// for loop ____ (int i = 0; i < 9; i++) { System.out.println("" + i); }
instanceof
Compares an object to a specified type
ClassName
//build a constructor in a class public ________ () { }
one
There can only be ____ package declaration for a file
primitive
Java does not pass a reference to a ______, but rather a copy of the value
parameters
Constructors can take _______
names
//iterate over array of int int[] numbers = {100,200,300}; for (String name:____){ System.out.println("Name" + name); }
new
//creating StringBuilder StringBuilder sb = ___ StringBuilder("hello");
default
// switch statement _____ (color) { case "Blue": shirt = "Blue" + shirt; break; case "Red": shirt = "Red" + shirt; break; _____: shirt = "White" + shirt; System.out.println("" + shirt); }
allocated
When an object is instantiated by using the new keyword, memory is ______ for the object
while
// while loop
_____ (x < 20) {
System.out.print("x: " + x);
x++;
System.out.print("
");
}
<=
Less than or equal to
StringBuilder
//creating StringBuilder _______ sb = new StringBuilder("hello");
()
// while loop
while _x < 20_ {
System.out.print("x: " + x);
x++;
System.out.print("
");
}
insert
//how to insert sb._____(::number::, " Fine");
append
//adding to a StringBuilder instance StringBuilder sb = new StringBuilder("hello"); sb.______(", how are you?");
private
The ______ keyword, applied to fields and methods, allows access only to other methods within the class itself
else
// if statement if (a == b) { System.out.println("True"); } ____ { System.out.println("False"); }
mutators
Methods that set the value of each field are called ______
!
Operator to invert boolean value
++
Increment operator
immutable
Removing the setter methods and replacing the no-arg constructor guarantees that some fields can be ________
130000.0
//what does this return? public class ObjectPassTest { public static void main(String[] args) { ObjectPassTest test = new ObjectPassTest(); Employee x = new Employee(); x.setSalary(120_000.00); test.foo(x); System.out.println("" + x.getSalary()); } public void foo(Employee e){ e.setSalary(130_000.00); e = new Employee(); e.setSalary(140_000.00); } }
memory
For Java objects, the value of the right side of an assignment is a reference to ______ that stores a Java object
new
//create an instance ClassName cn = ___ ClassName();
package
The _______ keyword is used in Java to group classes together
case
// switch statement switch (color) { _____ "Blue": shirt = "Blue" + shirt; break; _____ "Red": shirt = "Red" + shirt; break; default: shirt = "White" + shirt; }
++
// for loop for (int i = 0; i < 9; i__) { System.out.println("" + i); }
==
Equal to
name
//iterate over array of int int[] numbers = {100,200,300}; for (String ____:names){ System.out.println("Name" + name); }
immutable
The String class is ________
?:
Ternary
&&
Conditional-AND
reference
For Java objects, the value of the right side of an assignment is a ________ to memory that stores a Java object
if
// if statement ____ (a == b) { System.out.println("True"); } else { System.out.println("False"); }
public
The _____ keyword allows any class in any package to access the field or method
length
//how to get a length of StringBuilder sb.______()
>
Greater than
this
//build a class accessor public void setId (int id) { ____.Id = id; }
where
The scope of an object reference depends on ______ the object is instantiated
||
Conditional-OR
accessors
Methods that get the value of each field are called ______
switch
// switch statement _____ (color) { case "Blue": shirt = "Blue" + shirt; break; case "Red": shirt = "Red" + shirt; break; default: shirt = "White" + shirt; }
--
decrement operator
namespace
A package is implemented as a folder and, like a folder, provides a _______ to a class //com.example.domain +com |_+example |_+domain |_+Employee.java |_+Manager.java
value
The Java language (unlike C++) uses pass-by-_______ for all assignment operations
before
You can guarantee that an instance is fully populated with data _____ it is a valid employee object
;
// for loop for (int i = 0_ i < 9_ i++) { System.out.println("" + i); }
!=
Not equal to
Section 3
(50 cards)
runtime
The behavior of an object is determined by its ______ reference
Manager
//make code compile public static void main(String[] args){ Employee e = new Manager(); if (e instanceof Manager){ Manager m = ( _____ ) e; m.setDeptName("HR"); System.out.println(m.getDetails()); } }
setter
In an immutable class ______ methods are not provided for variables
inherited
In Java, constructors are not _______ from the parent class
default
Keyword used when a data field or method can be accessed within the same class or package
final
//make a Singleton public class SingletonClass { private static ____ SingletonClass instance = new SingletonClass(); private SingletonClass() {} public static SingletonClass getInstance() { return instance; } }
pattern
Design ______ are reusable solutions to common software development problems
overloading
Two rules apply to ________ methods: (1) argument lists must differ (2) return types can be different
final
All fields of an immutable class should be final
initializer
The static _______ block is a code block prefixed by the static keyword //example static boolean[] switches = new boolean[5]; _____ { System.out.println(""); for (int i=0; i<5; i++) { switches[i] = true; } }
constructors
In addition to overloading methods, you can overload _________
APIs
Static methods are useful for ____ that are not object oriented
variables
Static initialization blocks are used to initialize static _______
single
The Java programming language permits a class to extend only one other class. This is called _____ inheritance
new
The overloaded constructor is called based upon the parameters specified when the ____ is executed
hashcode
The general contract for Object states that if two objects are considered equal (using the equals method, then the integer _______ returned for the two objects should also be equal
inherit
When an existing class is subclassed, the new class created is said to ______ the characteristics of the other class
instanceof
The Java language provides the ________ keyword to determine an object's class type at run time
generic
It is a good practice to design and write methods that take the most ______ form of your object possible
subclassing
In Java, _______ is used to define a new class in terms of an existing one
shared
Static variables are useful for containing _____ data
methods
static _____ can be called even if the class they are declared in has not been instantiated
toString
The ______ method returns a String representation of the object
less
The overriding method cannot be ____ accessible than the method in the parent class
Static
_____ variables are variable s that can be accessed even if the class they are declared in has not been instantiated
protected
Keyword used when access is extended to subclasses that reside in a package different from that class that owns the protected feature
singleton
The ______ design pattern details a class implementation that can be instantiated only once
@Override
This annotation is used to instruct compiler that method annotated with _________ is an overridden method from super class or interface
initialization
Static methods are commonly used in place of constructors to perform tasks related to object ________
once
Static initialization blocks are executed _____ when the class is loaded
super
The _____ keyword may also be used to invoke a parent's method or to access a parent's (nonprivate) field //example ______ (empId, name, ssn, salary);
private
In an immutable class all field are declared _____ so that direct access is not allowed
final
To make an immutable class in Java declare the class as ______ so it cannot be extended
blocks
A class can contain one or more static initializer _____
static
The _____ modifier is used to declare fields and methods as class-level resources
import
A static _____ statement makes the static members of a class available under their simple name //example _____ static java.lang.Math.random; import static java.lang.Math.*; public class StaticImport { public static void main(String[] args) { double d = random(); } }
nontrivial
Consider using static initializers when ______ code is required to initialize static variables
order
The blocks are called in the ___ that they appear in the source code
downward
For ______ casts, the compiler must be satisfied that the cast is possible
loaded
Static variables are initialized when the containing class is first ______
extends
The keyword _____ creates the inheritance relationship //example public class Manager ____ Employee { }
private
Keyword used when a data field or method can be accessed only within the same Java class
Upward
______ casts are always permitted and do not require a cast operator
hashCode
It is necessary to override the ______ method whenever this the equals method is overridden
lang
The root class of every Java class is java._____.Object
public
Keyword used when you want fields and methods accessible anywhere in the class, package, subclasses and any other class
all
With static variables ___ objects instances share a single copy of any static variables
different
Qualify the location of the method with a class name if the method is located in a ______ class than the caller
same
If there are two objects x and y in any class, x is equal to y if and only if x and y refer to the ____ object
...
//make this varargs friendly public class Statistics { public float average(int___ nums) { int sum = 0; for (int x: nums) { sum += x; } return ((float) sum / nums.length } }
Section 4
(50 cards)
runtime
With enums no range checking overhead is incurred at ________
encapsulation
One benefit of using nested classes is increased __________ . Members can be declared private while still granting access to another nested "helper" class
sub
An abstract class can be ___classed
helper
Nested classes allow you to limit utilization of a _____ class to the enclosing top-level class
declared
Final fields (instance variables) must be either of the following: assigned a value when ________
specialized
Subclasses may not need to inherit a method implementation the method is __________
static
_________ nested classes can be instantiated before the enclosing outer class and, therefore, are denied access to all non static members of the enclosing class
common
Coding to a ______ base type allows for the introduction of new subclasses with little or no modification of any code that depends on the more generic base type
fields
Enums can have _____, methods and private constructors
local
Final variables can be ______ variables
cannot
An abstract class _______ be instantiated
synchronization
A benefit of immutable classes in Java is that an immutable object can boost performance of Java application by reducing ________ in code
constructor
In an immutable class all fields are initialized via a constructor
public
Interfaces are similar to abstract classes containing only _____ abstract methods
return
An abstract method can take arguments and _______ values
threads
The immutable nature of final variables eliminates any of the concerns that come with concurrent access by multiple ______
compile
Enumerations provide a ______-time range check
static
The ______ modifier can be combined with final to create an always-available, never-changing variable
cache
You can _____ immutable object and reuse them, much like String literals and integers
constant
Interfaces can contain _____ fields
GUI
Nested classes are commonly used in applications with _____ elements
private
Enums can fields, methods , and ______ constructors.
functionality
Use abstract methods to outline ________ required in child classes
pointing
A final object reference only prevents a reference from _______ to another object
abstract
A class can be declared as abstract by using the ______ class-level modifier
methods
Enums can fields, ______ , and private constructors.
arguments
An abstract method can take ______ and return values
switch
Enums can be used as the expression in a ______ statement
overridden
An abstract method is ________ in subclasses
constructor
Final fields (instance variables) must be either of the following: assigned a value in every _________
abstract
A method can be declared as abstract by using the __________ method-level modifier
thread
A benefit of immutable classes in Java is that their objects by default are _____-safe, and can be shared without synchronization in concurrent environment
classes
Final ______ may not be extended
new
You may not instantiate an enum instance with ____
constant
A field that is both static and final is considered a _______
body
An abstract method cannot have a method _____
parameters
Final variables can be method ______
Nesting
_______ small classes within top-level classes places the code closer to where it is used
inner
An ______ nested class is considered part of the outer class and inherits access to all the private members of the outer class
enum
//make an enumeration public _____ PowerState { OFF, ON, SUSPEND; }
methods
When inheriting from an abstract class, you must do either of the following: (1) Declare the child class as abstract (2) Override all abstract ______ inherited from the parent class.
nested
A ______ class is a class declared within the body of another class
initialized
Final variables may not change their values after they are _______
class
Interfaces outline methods that must be implemented by a _____
child
When inheriting from an abstract class, you must do either of the following: (1) Declare the _______ class as abstract (2) Override all abstract methods inherited from the parent class.
final
_______ methods may not be overriden
method
An abstract _______ must be declared in an abstract class
braces
No _______ are allowed when defining an abstract method
abstract
Java interfaces are used to define _____ types
together
If a class is useful to only one other class, then it is logical to embed it in that class and keep the two ______
Section 5
(50 cards)
collection
A _______ is a single object designed to manage a group of objects
generic
//example of a _______ class public class CacheAny<T> { private T t; public void add(T t) { this.t = t; } public T get() { return this.t; } }
ArrayList
Two implementations of the List interface are (1) _______ , (2) LinkedList
comma
A class can implement more than one interface in a _____-separated list at the end of the class declaration
arrow
The lambda expression is an argument list, the _____ token, and then a block or expression
LinkedHashSet
Three implementations of the Set interface are (1) TreeSet (2) HashSet (3) _________
generics
_________ provide flexible type safety to your code, reduce the need for casting with collections and move many common errors from run time to compile time
elements
List allows duplicate _______
elements
Objects in a collection are called ______
types
With generics, S and U are used if there are second or third ______
block
The lambda expression is an argument list, the arrow token, and then a _____ or expression
List
_____ is an ordered collection of elements
new
//Make an Anonymous inner class Z04Analyzer.searchArr(strList01, ___ StringAnalyzer() { @Override public boolean analyze(String target, String searchStr) { return target.contains(searchStr); } } });
interface
Any class that implements an interface can be referenced by using that ________
HashTable
Three implementations of the Map interface are (1) HashMap (2) ______ (3) TreeMap
adding
List behaviors include (1) ____ elements at a specific index (2) Getting an element based on an index (3) Removing an element based on an index (4) Overwriting an element based on an index (5) Getting the size of the list
interfaces
List, Set and Map are _______ in Java
extend
Interfaces can _______ interfaces
LinkedList
Two implementations of the List interface are (1) ArrayList (2) _______
default
In an interface the ______ keyword allows you to provide fully implemented methods to all implementing classes
argument
The lambda expression is an ______ list, the arrow token, and then a block or expression
element
With generics, E means ______
harming
Default methods can be added or changed without ______ API hierarchies
methods
You may not declare ______ as private or protected in an interface
util
The Collections classes are all stored in the java.____ package.
cache
//example of a simple ______ class public class CacheString { private String message; public void add(String message){ this.message = message; } public String get(){ return this.message; } }
type
With generics, T means _____
right
When instantiating a generic class there is no need to repeat types on the _____ side of the statement //example CacheAny<String> myMessage = new CacheAny<>();
lambda
A ______ expression can be substituted for an anonymous inner class
HashMap
Three implementations of the Map interface are (1) ______ (2) HashTable (3) TreeMap
List
______ behaviors include (1) adding elements at a specific index (2) Getting an element based on an index (3) Removing an element based on an index (4) Overwriting an element based on an index (5) Getting the size of the list
field
When you declare a _____ in an interface, it is implicitly public, static and final
value
With generics, V means _____
<String>
//Write generic of the following CacheString myMessage = new CacheString(); CacheAny_____ myGenericMessage = new CacheAny_____();
extends
If you use both extends and implements, ________ must come first
expression
The lambda expression is an argument list, the arrow token, and then a block or ________
abstract
Because all methods are implicitly abstract in an interface it is redundant to use the _____ modifier
methods
Java 8 allows static ________ in an interface
implementing
A utility class that references that interface can prices any ______ class
TreeMap
Three implementations of the Map interface are (1) HashMap (2) HashTable (3) ________
TreeSet
Three implementations of the Set interface are (1) ______ (2) HashSet (3) LinkedHashSet
can
Interfaces _____ be used as a reference type
primitives
_______ are not allowed in a collection
()
//Write generic of the following CacheString myMessage = new CacheString(); CacheAny<String> myGenericMessage = new CacheAny<String>__;
HashSet
Three implementations of the Set interface are (1) TreeSet (2) ______ (3) LinkedHashSet
key
With generics, K means _____
lambda
______ expressions can be treated like variables
boolean
Lambda expressions have two variables and return a _______
Collections
The ______ API relies heavily on generics for its implementation
ArrayDeque
The implementation of Deque is ________
Section 6
(50 cards)
Unbox
//_____ Integer collection for (Integer partNumberObj:partList) { int partNumber = partNumberObj; System.out.println("Part number: " + partNumber); }
Deque
A collection that can be used as a stack or a queue
variable
//use of lambdas as a ______ Predicate<Person> allPilots = p -> p.getAge() >= 23 && p.getAge() <= 65; p1.stream().filter(allPilots).forEach(p -> rob.roboCall(p));
Value
In a Map interface the ______ is stored in the element associated with the key
Key
In a Map interface the ______ is a unique identifier for each element in a collection
TreeMap
//implement a TreeMap public class MapExample { public static void main(String[] args) { Map<String, String> partList = new ______<>(); //.... } }
index
In an ArrayList elements can be overwritten and accessed or inserted based on _______
<>
//implement a TreeMap public class MapExample { public static void main(String[] args) { Map<String, String> partList = new TreeMap__(); //.... } }
positive
In a Comparable interface implementation if the return number is ________ the parameter comes after the current element
zero
In a Comparable interface implementation if the return number is ________ the parameter is equal to the current element
ArrayDeque
//example of a _______ public class Teststack { public static void main(String[] args) { Deque<String> stack = new ________<>(); stack.push("one"); } }
pipeline
The Stream class converts a collection to a _______
zero
A stream pipeline consists of a source, ____ or more intermediate operations or one terminal operation //example tList.stream().filter(t -> t.getState().equals("CA")).forEach(SalesTxn::printSummary);
iterate
You can ______ through Set elements to access them
add
A queue provides FIFO (first in, first out) operations with ____(e) and remove() methods
stream
The ______ method opens up a whole host of new operations on collections //example p1._____().filter(p -> p.Age() >= 23).forEach(p -> rob.roboCall(p));
primitives
Auto boxing and unboxing are useful for moving between objects and _______
Builder
//example of the ______ pattern people.add( new Person.______() .givenName("Betty") .surName("Jones") .age(85) .gender(Gender.FEMALE) );
removing
List behaviors include (1) adding elements at a specific index (2) Getting an element based on an index (3) ______ an element based on an index (4) Overwriting an element based on an index (5) Getting the size of the list
queue
A ______ provides FIFO (first in, first out) operations with add(e) and remove() methods
::
//make reference to a static method ContainingClass__staticMethodName
chaining
Using method _______ you can use multiple methods in one statement
Map
The _____ interface is a collection that stores multiple key-value pairs
getting
List behaviors include (1) adding elements at a specific index (2) _____ an element based on an index (3) Removing an element based on an index (4) Overwriting an element based on an index (5) Getting the size of the list
stack
A ______ provides LIFO (last in, first out) operations with push(e) and pop() methods
Set
A ______ is an interface that contains only unique elements and has no index
Streams
_______ are a sequence of elements on which various methods can be chained
compare
Comparator is implemented by using the ______ method
sorting
The Comparator interface enables you to create and use numerous ______ options
parallel
Streams can be serial or _____
lambda
Within a ______ expression you can use a method reference in the following situations: Reference to a static or instance method or in reference to a constructor (i.e. ClassName::new)
overwriting
List behaviors include (1) adding elements at a specific index (2) Getting an element based on an index (3) Removing an element based on an index (4) _______ an element based on an index (5) Getting the size of the list
chain
A _____ of operations can occur only once with a stream
TreeSet
Comparable and Comparator interfaces can be used with sorted collections, such as _______ and TreeMap
source
A stream pipeline consists of a ______, zero or more intermediate operations or one terminal operation
()
//implement a TreeMap public class MapExample { public static void main(String[] args) { Map<String, String> partList = new TreeMap<>__; //.... } }
ArrayList
The _______ list automatically grows if elements exceed initial size
comparator
The Comparator interface enables you to create multiple ________ classes
negative
In a Comparable interface implementation if the return number is ________ the parameter comes before the current element
TreeSet
Of the Set interfaces _______ provides a sorted implementation
Comparable
The _______ interface overrides the compareTo method and provides only one sort option
deque
A ______ is a "doubled-ended queue"
predicate
The filter method uses ________ lambdas to select items
Streams
_______ are immutable, can be serial, parallel and after their elements are consumed they are no longer available. Also, a chain of operations can occur only once with it.
getting
List behaviors include (1) adding elements at a specific index (2) Getting an element based on an index (3) Removing an element based on an index (4) Overwriting an element based on an index (5) _____ the size of the list
remove
A queue provides FIFO (first in, first out) operations with add(e) and _____() methods
Comparator
The _______ interface is implemented by using the compare method, enables you to create multiple _________ classes and enables you to create and use numerous sorting options
<>
//Use generics to add compile time check List partList = new ArrayList(3); List<Integer> partList = new ArrayList__(3);
TreeMap
Comparable and Comparator interfaces can be used with sorted collections, such as TreeSet and ________
null
A HashMap implementation justlike Hashtable except that it accepts ____ keys and values
Section 7
(50 cards)
predicate
A _______ is an expression that returns a boolean
comparing
The _______ method allows you to specify any field to sort on based on a method reference or lambda //_(Function<?superT,?extendsU> keyExtractor)
min
//in stream return smallest //element of this stream //according to Comparator __(Comparator<? super T> comparator)
count
In a stream pipeline the _______ method returns the number of elements in it
invocations
Nondeterministic search method results may vary between _______. Useful when employing parallelism.
max
//in stream return biggest //element of this stream //according to Comparator __(Comparator<? super T> comparator)
Function
//example of a ______ package java.util._____; public interface ______<T, R> { public R apply(T t); }
double
//complete primitive type return package java.util.function; public interface ToDoubleFunction<T> { public ____ applyAsDouble(T t); }
supplier
In the context of a stream this provides an instance of a T (such as a factory)
findFirst
In a stream pipeline the _____ short-circuit method returns the first element that meets the specified criteria
predicate
//example of _____ package java.util.function; public interface ______<T> { public boolean test(T t); }
T
//take class as input and return //object of the same class package java.util.function; public interface UnaryOperator<T> extends Function<T, T> { @Override public __ apply(T t); }
extends
//accept this & any child types ? ______ T
allMatch
In a stream pipeline the ______ short-circuit method returns true if all the elements meet the criteria
consume
Primitive interfaces can return and ______ a primitive
intermediate
The peek method is great for printing _______ results
util
Optional class is found in java.____
optimized
Lazy operations can be _______ and perform only required operations
result
A terminal operation in a store pipeline produces a _____ or side effect
super
//accept this & any parent types ? _____ T
short-circuit
//stream methods //each below is a Terminal ___ findFirst() --- findAny() --- anyMatch() --- allMatch() --- noneMatch()
sorted
In a stream the _____ method returns a stream consisting of the elements sorted according to natural order
peek
The ____ method performs the operation specified by the lambda expression and returns the elements to the stream. //code _(Consumer<? super T> action)
noneMatch
In a stream pipeline the _____ short-circuit method returns true if none of the elements meet the criteria
R
//process a primitive type package java.util.function; public interface DoubleFunction<R> { public __ apply(double value); }
Primitive
______ versions of map are mapToInt(), mapToLong(), mapToDouble()
average
In a stream pipeline the _____ method returns an optional describing the arithmetic mean of the stream elements
Supplier
//example of a _____ package java.util.function; public interface _______<T> { public T get(); }
boolean
//complete a BiPredicate package java.util.function; public interface BiPredicate<T, U> { public ______ test(T t, U u); }
primitives
OptionalDouble, OptionalInt and OptionalLong are Optional ________
functional
Lambda expressions rely on ______ interfaces
consumer
An expression that performs operations on an object passed as argument and has a void return type
sum
In a stream pipeline the ____ method returns the sum of elements in this stream
return
Primitive interfaces can ______ and consume a primitive
consumer
//example of a _____ ______<SalesTxn> buyer = t -> System.out.println("Id: " + t.getTxnId() + " Buyer: " + t.getBuyer().getName()); System.out.println("== Buyers - Lambda"); tList.stream().forEach(buyer); System.out.println("== First Buyer - Method"); buyer.accept(first);
intermediate
//stream methods //below: examples of _____ //operations filter() --- map() --- peek()
map
A ____ takes one Function as an argument. A Function takes one generic and returns something else //code ___(Function<? super T, ? extends R> mapper)
function
In the context of a stream this transforms a T to a U
optional
The findAny method returns an _______<T>
findAny
The nondeterministic search method _____ returns the first element found that meets the specified criteria
Comparator
//return sort according 2 comp sorted(______<? super T> comparator)
side
A terminal operation in a store pipeline produces a result or ____ effect
thenComparing
The _____ method can be added to the comparing method to do a multilevel sort on the elements in the stream
terminal
//stream methods //below: examples of ____ //operations forEach() --- count() --- sum() --- average() --- min() --- max() --- collect()
isPresent
In the Optional class if a value is present, _______ returns true
get
In the Optional class ____ returns the value
optional
A container object that may or may not contain a non-null value
reversed
The _____ method can be appended to a pipeline, thus reversing the sort order of the elements in the stream
anyMatch
The nondeterministic search method _____ returns true if any elements meet the criteria
required
Lazy operations can be optimized and perform only ______ operations
Section 8
(50 cards)
IOException
//complete try { in = new FileInputStream("missing file.txt"); } catch (______ e) { System.out.println(e.getMessage()); } finally { try { if(in != null) in.close(); } catch(IOException e) { System.out.println("Failed to close file"); } }
Exception
A catch clause is passed as a reference to a java.lang.____
groupingBy
The ______ method of the Collectors class operates on input elements of type T, grouping elements according to a classification function, and returning the results in a map //code _(Function<?superT,?extendsK>classifier)
inheritance
The type alternatives that are separated with vertical bars cannot have an _______ relationship
throws
Declaring an exception means to add a _______ clause to a method declaration, indicating that the method may fail to execute in a specific way.
catch
//complete try { InputStream in = new FileInputStream("missing file.txt"); } __ (Exception e) { System.out.println("Something went wrong"); }
assertions
Do not use ____ to check the parameters of a public method
specific
You should always catch the most ______ type of exception
internal
An _______ invariant is a "fact" that you believe to be true at a certain point in the program
side
Do not use methods that can cause _____ effects in the assertion check
try-with-resources
//example of _______ try(InputStream in = new FileInputStream("missing file.txt")) { System.out.println("File open"); int data = in.read(); } catch ...
handling
_______ a exception means that you must add in a code block to handle the error
|
//perform multi-catch try () { } catch (ClassNotFoundException _ IOException e) { System.out.println(); }
class
A _____ invariant is one that an object must satisfy in order to be a valid member of a class
exception
You may declare that a method throws an ______ instead of handling it
Exception
Sometimes the operation that you want to perform in your finally block may itself cause an ______ to be generated
true
An invariant is something that should always be ______
Exception
You can create custom exception classes by extending _____ or one of its subclasses
flatMap
Use the ____ method to flatten data in a stream. Can be used to convert data into a stream
exception
Declaring an ______ means that you declare that a method may fail to execute successfully
try-catch
Handling an exception means that you use a ________ statement to transfer control to an exception-handling block when an exception occurs.
collect
The ______ method allows you to save the result of a stream to a new data structure //example stream().collect(Collectors.toList());
internal
//ex. of __ invariant use int x = num; if (x > 0) { System.out.print("+"); } else if (x == 0) { System.out.print("0"); } else { assert (x > 0); }
exception
The throw statement is used to throw an instance of _______
assertions
Use _______ to document and verify the assumptions and internal logic of a single method
assert
//complete assertion _____ booleanExpression;
close
You always want to _____ open resources
resources
The try-with-______ statement is a try statement that declares one or more _______
of
The Stream.__ method allows you to easily create a stream //example Stream.of("Monday","Tuesday").filter(s -> s.startsWith("T")).forEach(s -> System.out.println("Matching Days: " + s));
finally
//complete try { in = new FileInputStream("missing file.txt"); } catch (IOException e) { System.out.println(e.getMessage()); } __ { try { if(in != null) in.close(); } catch(IOException e) { System.out.println("Failed to close file"); } }
:
//descriptive assertion assert booleanExpression _ expression;
getMessage()
When you only want to know what the error message is and do not want the full stack track use the _______ method
control
//ex. of ____ flow invariant switch(suit) { case Suit.CLUBS: // break; case Suit.DIAMONDS: // break; default: assert false: "Unknown"; break; }
library
Production-quality applications should use a logging _____ instead of printing debug message to the screen
throws
//complete public static int readByte() _____ IOException {...}
control
Errors can occur because of factors beyond the _____ of the application
partitioningBy
The _____ method of the Collectors class partitions the input elements according to a Predicate //code _(Predicates<?superT>predicate)
finally
A _______ clause runs regardless of whether or not an Exception was generated
unchecked
The two main categories of exceptions are checked exceptions, which must be "handled or declared" or ________ exceptions, which are not typically "handled or declared"
Trace
The method printStack____() helps to track down the cause of the exception
applications
Errors must be handled to create reliable ______
Throwable
The java.lang.____ class is the parent class for Exception and it outlines several methods that you may use.
AutoCloseable
Any class that implements java.lang._____ can be used as a resource
handled
The exceptions that methods may throw must still be ______
averagingDouble
The ______ method of the Collectors class produces the arithmetic mean of a double-valued function applied to the input elements //code averagingDouble(ToDoubleFunction<? super T> mapper)
checked
The two main categories of exceptions are ________ exceptions, which must be "handled or declared" or unchecked exceptions, which are not typically "handled or declared"
errors
_______ should be an exception and not the expected behavior
try
//complete __ { InputStream in = new FileInputStream("missing file.txt"); } catch (Exception e) { System.out.println("Something went wrong"); }
multi
The new ____-catch clause reduces the amount of code you must write by eliminating the need for many catch clause
joining
The ___ method of the Collectors class concatenates the input elements into a String, in encounter order
Section 9
(50 cards)
Period
________ is a class that holds a date-based amount
close
//auto closed in try-w-r void _____();
System
The _____ class in the java.lang package has three static instance fields: out, in, and err.
ZoneOffset
______: Extends ZoneId; specifies the actual time different from UTC
LocalDate
The java.time API defines two classes includes: (1) ______ (2) LocalTime
skip
//discard n bytes long ____(long n);
LocalTime
Questions that you can answer with _______: (1) When is my lunch time? (2) Is lunch time in the future or past? (3) What is the time 1 hour 15 minutes from now? (4) How many minutes until lunch time? (5) How many hours until bedtime? (6) How do I keep track of just the hours and minutes?
ZoneId
_______: is a specific location or offset relative to UTC
files
Typically, a developer uses input and output in three ways: (1) _____ and directories (2) console (3) socket-based sources
byte
Java technology supports two types of streams: character and _____
LocalTime
The java.time API defines two classes includes: (1) LocalDate (2) ______
OffsetDateTime
___________ class stores a LocalDateTime and ZoneOffset
ZoneRules
______: is the class used to determine offsets
JDK
Each time zone (ZoneID) has a set of rules that are part of the _____
close
//terminate open stream void ______();
write
//3 byte write methods void _(int c) void _(byte[] buffer) void _(byte[], int offSet, int length)
Instant
The ______ class stores an instant in time on the time-line
socket
Typically, a developer uses input and output in three ways: (1) files and directories (2) console (3) _____-based sources
available
//get bytes avail in stream int _______();
new
//chain streams FileReader //to BufferedFileReader try (BufferedReader bufInput = ___ BufferedReader(__ FileReader(args[0]));
class
//ex. of ____ invariant public class PersonClassInvariant { String name; String son; int age; private void checkAge() { assert age >= 18 && age < 150; } public void changeName(String fname) { checkAge(); name=fname; } }
standard
The System.out filed is a static instance of PrintStream object that enables you to write to _____ output
LocalDateTime
Questions you can answer the following questions with _______: (1) When is the meeting with corporate? (2) When does my flight leave? (3) When does the course start? (4) If I move the meeting to Friday, what is the date? (5) If the course starts at 9 AM on Monday and ends at 5 PM on Friday, how many hours am I in class?
offset
The three basic byte read methods are: (1) int read() (2) int read( byte[] buffer) (3) read(byte[] buffer, int _____, int length)
one
A program uses an input stream to read data from a source, ____ item at a time
DateTimeFormatter
________ produces formatted date/times
from
The System.in field is a static instance of an InputStream object that enables you to read ____ standard input
ea
//turn on assertions java -__ MyProgram
streams
Input and output of character data is handled by readers and writers in ________
+=
//count bytes read while ((read = fis.read(b)) != -1) { fos.write(b); count __ read; }
LocalDateTime
______ is a combination of LocalDate and LocalTime
source
An I/O stream represents an input _____ or an output destination
destination
An I/O stream represents an input source or an output _______
PrintStream
The println and print methods are part of the java.io._____ class
character
Java technology supports two types of streams: _______ and byte
disabled
If assertion checking is _____, the code runs as fast as it would if the check were not there
byte
Input and out of ____ data is handled by input streams and output streams
byte[]
The three basic byte read methods are: (1) int read() (2) int read( ____ buffer) (3) read(byte[] buffer, int offset, int length)
err
The System.___ field is a static instance of a PrintStream object that enables you to write to standard error
console
Typically, a developer uses input and output in three ways: (1) files and directories (2) _____ (3) socket-based sources
TemporalUnit
_____ is an interface representing a unit of time
stream
An I/O ______ can represent many different kinds of sources and destinations, including disk files, devices, other programs, and memory arrays
()
The three basic byte read methods are: (1) int read__ (2) int read(byte[] buffer) (3) read(byte[] buffer, int offset, int length)
sink
A program uses an output stream to write data to a ____, one item at time
Duration
_______ is a class that stores a time-based amount
write
//basic write void _(int c) void _(char[] cbuf) void _(char[] cbuf, int offset, int length) void _(String string) void _(String string, int offset, int length)
LocalDate
Questions that you can answer with _______: (1) Is it in the future or past? (2) Is it in a leap year? (3) What day of the week is it? (4) What is the day a month from now? (5) What is the date next Tuesday?
I/O
Java defines an ___ channel as a stream
read
//3 basic read methods int _() int _(char[] cbuf) int _(char[] chuff, int offset, int length)
flush
//force write to the stream void _____();
Section 10
(50 cards)
interface
The Path ______ is "link aware"
transient
Some object classes are not serializable because the represent ______ operating system-specific information
one
The element returned by endIndex is ___ less than the endIndex value
isWritable
//verify write access to file //using Files Class _______(Path)
deserialization
After _______ , the serialVersionUID is checked to verify that the classes loaded are compatible with the object being deserialized
graph
The tree of an object's fields constitutes the object _____
overloaded
The print and println methods are _______ for most primitive types and for char[], Object and String
resolve
The ____ method is used to combine two paths
NotSerializableException
If the object graph contains a non-serializable reference, a ________ is thrown and the serialization operation fails
println
The ____ methods print the argument and a newline character (
)
detects
Every Path method either: (1) ____ what to do when a symbolic link is encountered, or (2) Provides an option enabling you to configure the behavior when a symbolic link is encountered
transient
Fields that should not be serialized or that do not need to be serialized can be marked with the keyword ______
relative
A path is either _____ or absolute
in
//chain a buffered reader //to an input stream that //takes the console input try (BufferedReader in = new BufferedReader(new InputStreamReader(System.__)) { ... }
toString
The print and println methods call the ____ method on the argument
serialVersionUID
A serializable class can declare its own serialVersionUID by explicitly declaring a field named _______ as a static final and of type long
symbolic
Hard links are more restrictive than _____ links
serialVersionUID
During serialization, a version number, _________, is used to associate the serialized output with the class used in the serialization process
serializable
When a field reference an object, the fields of the referenced object are also serialized, if that object's class is also _______
getPath
To obtain a Path object, obtain an instance of the default file system, and then invoke the _____ method
running
A non-persisted object exists only as long as the Java Virtual Machine is _____
Path
The _____ interface defines the methods used to locate a file or a directory in a file system
exists
Before you can access a file or directory, you should first access the file system to determine whether it exists using the ______ Files methods
aware
Files class is also link _____
Path
java.nio.file.___: Locates a file or a directory by using a system-dependent path
hard
____ links are more restrictive than symbolic links
FileSystem
java.nio.file.____: Provides an interface to a file system and a factory for creating a Path and other objects that access a file system
persistence
Saving data to some type of permanent storage is called ________
Path
Use the _____ interface to operate on a path using: normalize, tours, toAbsolutePath, subpath, resolve, relativize
Path
The java.nio.file.____ interface provides the entry for the NIO.2 file and directory manipulation
normalize
The ______ method removes any redundant elements, which includes any "." or "directory/.." occurrences
fields
When an object is serialized, only the ____ of the object are preserved
Path
Static methods in the class read, write, and manipulate files and directories represented by _____ objects
Files
java.nio.file.Files: Using a Path, performs operations on files and directories
own
An object being serialized (and deserialized) can control the serialization of its ____ fields
serialization
Java _____ is the standard mechanism for saving an object as a sequence of bytes that can later be rebuilt into a copy of the object
absolute
A path is either relative or _________
get
Using the Path interface to access the components of a path use the following: __FileName, __Parent, __Root, __NameCount
relative
A ______ path must be combined with another path in order to access a file
subpath
A portion of a path can be obtained by creating a subpath using the _____ method: //example Path subpath(int beginIndex, int endIndex);
The ____ methods print the argument without a newline character
Path
Use the ____ interface to compare paths using: startsWith, endsWith, equals
InvalidClassException
If the receiver of a serialized object has loaded classes for that object with different serialVersionUID, deserialization will result in an ______________
root
An absolute path always contains the _____ element and the complete directory list required to locate the file
Path
A ______ object represents the concept of a file or a director location
IOException
All the methods that access the file system throw ______ or a subclass
Files
The java.nio.file._____ class is the primary entry point for operations on Path objects
isReadable
//verify read access to file //using Files Class _______(Path)
provides
Every Path method either: (1) detects what to do when a symbolic link is encountered, or (2) ____ an option enabling you to configure the behavior when a symbolic link is encountered
io
To serialize an object of a specific class, the class must implement the java.__.Serializable interface
Section 11
(50 cards)
static
____ synchronized methods use the classes' monitor
Future
The ___ interface is used to obtain the results from a Callable's V call() method //example __<V> ___ = es.submit(callable); try { V result = __.get(); } catch (ExecutionException|InterruptedException ex) { }
ExecutorService
An ________ is used to execute tasks
process
A _______ is an area of memory that contains both code and data
readAllLines
//load a file into an //ArrayList Files.___(file);
operations
_____ performed in one thread may not appear to execute in order if you observe the results from another thread
concurrently
Instance and static fields might be changed _______ by multiple threads
ExecutorService
Shutting down an ______ is important because its threads are nondaemon threads and will keep your JVM from shutting down
Callable
The ____ interface: (1) Defines a task submitted to an ExecutorService (2) Is similar in nature to Runnable, but can: Return a result using generics, throw a checked exception //example package java.util.concurrent; public interface __<V> { V call() throws Exception; }
list
//get a list of all of the files Files.__(Paths.get("."))
delete
//delete file/dir/link w/ //exceptions Files.__(path)
this
Synchronized methods use the monitor for the ______ object //example synchronized(___) { }
starvation
A situation where a thread attempts to access a resource that it can never access
debugging
__ threads can be difficult because the frequency and duration of time each thread is allocated can vary for many reasons
lines
//convert BufferedReader //into a stream bReader.____()
multiple
Classes should continue to behave correctly when accessed from _____ threads
isExecutable
//verify execute ability //using Files Class _______(Path)
createFile
//create a file Files._____(Path dir);
working
Every thread has a ______ memory in which it keeps its own copy of variables that it must use or assign
move
//change location of file/dir Files.__(src, trg, REP_EX);
blocks
Synchronized _____ must specify which object's monitor to lock or unlock
deleteIfExists
//delete file/dir/link w/ //no exceptions Files.___(path)
CPUs
Machines have different counts and speeds of ____
isSameFile
//verify method tests to //to see whether two paths //point to the same file ______(Path, Path)
slice
The amount of time each task is given
walk
//walk a dir structure Files.__(Paths.get("."))
main
There are several actions that will synchronize a thread's working memory the _____ memory: (1) A volatile read or write of a variable (2) locking or unlocking a monitor (3) the first and last action of a thread (4) actions that start a thread or detect that a thread has terminated
shared
Static and instance fields are potentially shared by threads
synchronize
To ensure consistent behavior in your threads, you must _____ their actions
cached
A ____ thread pool ExecutorService: (1) Creates new threads as needed (2) Reuses its threads (3) Terminates threads that have been idle for 60 seconds
createDirectory
//create a directory Files._____(Path dir);
Runnable
Tasks can be (1) java.lang._____ or java.util.concurrent.Callable
heap
Instance and static fields are created in an area of memory known as _____ space
deadlock
_____ is a situation where thread A is blocked waiting for a condition set by thread B, but thread B is also blocked waiting for a condition set by thread A
createDirectories
//create directories that //don/t exist, from top //to bottom Files.__(Paths.get("/home/foo/bar/example"));
monitor
Each object in Java is associated with a _______, which a thread can lock or unlock
atomic
A single statement in the Java language is not always ______
livelock
____ is a condition where a thread is not blocked, but cannot move forward because an operation it continually retries fails
Callable
Tasks can be (1) java.lang.Runnable or java.util.concurrent.___
copy
//replicate a file or dir Files.__(source, target, REPLACE_EXISTING, NOFOLLOW_LINKS);
thread
A _____ is a scheduled execution of a process
get
Because the call to Future.__() will block, you must do one of the following: (1) Submit all your work to the ExecutorService before calling any Future._() methods (2) Be prepared to wait for that Future to obtain the result (3) Use a non-blocking method such as Future.isDone() before calling Future.get() or use Future.get(long timeout, TimeUnit unit), which will throw a TimeoutException if the result is not available within a given duration
scheduling
Thread ____ is handled by an operating system and operating systems may use different scheduling algorithms
Executors
Implementing instances can be obtained with _____ //example ExecutorService es = ____.newCachedThreadPool();
thread
Because synchronized blocks and methods are used to restrict a section of code to a single _____, you are potentially creating performance bottlenecks
symbolic
A _____ link is a special file that serves as a reference to another file
thread
The following types are always are always ____-safe: (1) local variables (2) method parameters (3) exception handler parameters (4) immutable data
fixed
A ____ thread pool ExecutorService: (1) Contains a fixed number of threads (2) Reuses its threads (3) Queues up work until a thread is available (4) Could be used to avoid over working a system w/ CPU-intensive tasks
synchronized
The _____ keyword is used to create thread-safe code blocks
block
A synchronized code _____: (1) causes a thread to write all of its changes to main memory when the end of the block is reached (2) is used to group blocks of code for exclusive execution
Section 12
(50 cards)
reduction
An operation that takes a sequence of input elements and combines them into a single summary result by repeated application of a combining operation
process
The data being analyzed may require varying amounts to time to _____
stateless
//mutate the ____ way List<Employee> newList02 = new ArrayList<>(); newList02 = eList.parallelStream() .filter(e -> e.getDept().equals("Eng")) .collect(Collectors.toList());
subsets
To keep multiple threads busy each thread will have many ____ queued
CPU
Bottlenecks can occur when a single-threaded application uses only a single ___
util
The java.___ collections are not thread-safe
lambda
A stateful ____ is one whose result depends on any state which might change during the execution of the stream pipeline
last
Sequential and parallel methods may be called in a pipeline--whichever method is called ____, will be applied to the stream
lock
A thread can ____ multiple monitors simultaneously by using nested synchronized blocks
threaded
//single-_____ example //1 Gig int[] data = new int[10241024256]; for (int i = 0; i < data.length; i++) { data[i] = ThreadLocalRandom.current().nextInt(); } int max = Integer.MIN_VALUE; for (int value: data) { if (value > max) { max = value; } } System.out.println("Max value found:" + max);
read
Your data should be immutable or ____-only when used with stream pipelines
stateful
//mutate the ______ way //doesn't parallelize List<Employee> newList01 = new ArrayList<>(); eList.parallelStream().filter(e -> e.getDept().equals("Eng")) .forEach(e -> newList01.add(e));
deterministic
A ______ algorithm is an algorithm which, given a particular input, will always produce the same output //example ...paralle.().sum()
deadlock
//below will cause _____ synchronized(obj1) { synchronized(obj2) { ... } } synchronized(obj2) { synchronized(obj1) { ... } }
ForkJoinTask
A _______ typically creates more _______ instances until the data to processed has been subdivided adequately
parallel
A simple ____ solution breaks the data to be processed into multiple sets: one data set for each CPU and one thread to process each data set
RecursiveTask
With java.util.concurrent.ForkJoinTask<V>, when a task does need to return a result developers typically use a _________
avoid
When using Fork-Join, ____ I/O or blocking operations, know your hardware and know your problem
work
By subdividing the data to be precessed until there are more subsets than threads, we are facilitating "___-stealing."
overhead
Overly subdividing the data to be processed can cause unnecessary ______
collections
To use _____ in a thread-safe fashion: (1) use synchronized code blocks for all access to a collections if writes are performed (2) java.util.Collections.synchronizedList(List<T>) (3) Use the java.util.concurrent collections
concurrent
The java.util.___ package contains a numbers of classes that help with applications that are running at the same time
divide
To keep multiple threads busy _____ the data to be processed into a large number of subset
different
The larger the data set, the more likely the two code blocks will produce a _____ result
stateless
Operations parameters must be ______, this enables correct operation sequentially or in parallel. Best to banish side effects completely
atomic
java.util.concurrent.___ package will lock free thread-safe variables
queue
To keep multiple threads busy assign the data subsets to a thread's processing _____
time
Non-Java tasks require CPU _____
streams
Parallel _____ may provide better performance
parallelStream
//Make parallel stream double result = eList.____()
power
If you do not leverage threads in some way, only a portion of your system's processing ____ will be utilized
ForkJoinTask
A _______ object represents a task to be executed: (1)
documentation
When creating code to run inside of another piece of software you much read the product's ________ to discover whether threads will be created automatically
Builders
Stream pipelines are like _______
different
CPUs may run at ____ speeds
RecursiveTask
//__ example public class FindMaxTask extends ____<Integer> { private final int threshold; private final int[] myArray; private int start; private int end; public FindMaxTask(int[] myArray, int start, int end, int threshold) { // copy parameters to fields } protected Integer compute() { // shown later } }
steal
If a thread finishes all its subsets early, it can ____ subsets form another thread
RecursiveAction
With java.util.concurrent.ForkJoinTask<V>, when a task does not need to return a result developers typically use a _________
CyclicBarrier
The _____ is a class that blocks until a specified number of threads are waiting for the thread to complete
optimal
You must determine the _____ size of the work to add to each thread's processing queue.
atomic
There is no need to use the synchronized keyword with ____ variables
Join
A huge number of tasks are created and processed by a small number of threads in a Fork-___ pool
ForkJoinPool
A ______ is used to execute a ForkJoinTask. It creates a thread for each CPU in the system by default
contention
Resource _____ is when two or more tasks waiting for exclusive use of a resource
subdividing
Insufficiently ____ the data can result in underutilization of CPUs
availableProcessor
//detect number of //processors int count = Runtime.getRuntime().__();
intensive
If your tasks are compute-_____ as opposed to I/O _______, the number of parallel tasks should not greatly outnumber the number of processors in your system
i/o
Blocking ____ operations things can't happen because they are waiting for disk or network data transfer
fork
____/join is great, but too low level, has a lot of boilerplate code and stream uses ____/join under the hood
associative
If the combining function is ______, reduction parallelized cleanly //examples sum, min, max, average
Section 13
(34 cards)