Section 1
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Primitive Types
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Date created
Mar 1, 2020
Cards (72)
Section 1
(50 cards)
Primitive Types
int, double, short, long, float, byte, boolean, char
Constructor
special method that constructs instance of classes
JRE
Java Runtime Environment: JVM + libraries
Difference between break and continue
Break ceases the logic of current block's code Continue also ceases the logic of the current block's code but then returns to the top of the loop
String
class that is implemented using an array of characters. It is also immutable which means it can't be changed
Method vs Function
Method is attached to an object, function is not
Handle Keywords
try, catch, finally, throw, throws
Static/Class Scope
One copy of the variable and/or method
Checked vs Unchecked
Checked: the compiler will give a syntax error if the exception is not handled Unchecked: the compiler does NOT give a syntax error if the exception is not handled
Overloading
When you have multiple methods with the same name but with different parameter lists
JDK
Java Development Kit: JRE + Devtools (debuggers, compiler, etc.)
Heap
Live portion of memory
Garbage collector
Looks through the heap and deallocates memory for us
Object
group of states (variables) and actions/behaviors (methods)
Three Ways to Change the Parameter List
Change the order of parameters, number of parameters, or the data types
Array
series of data entries of the same type
Short Circuit Operators
|| && purpose is to speed up logic called short-circuit operator because it conditionally evaluates its second operand. If the first operand evaluates to false, the value of the expression is false, regardless of the value of the second operand. && It evaluates to true if and only if both operands of logical AND are true. If either or both operands are false, it evaluates to false. || evaluates to true if either or both of its operands are true. If both operands are false, it evaluates to false. *
What does the "super" keyword target?
The parent
Instantiate vs Initialize
Instantiate: creation of an object Initialize: creating of a variable
Deprecated
The support for that method has been discontinued. Will still work for backwards compatibility but will let the developer know they should be switching to a new system
Which scopes give default values?
Class/Static and Object/Instance
Static
Value belongs only to the class. To avoid creating instances
Why are Strings immutable?
All string literals are put into the String Pool. If you were to change a string within that pool, it would change all references to that string object
Casting
Taking an Object of one particular type and "turning it into" another Object type
Shadowing
When a child inherits from a parent, it stores two copies of a variable with the same name. The parent's variable becomes harder to access
Flow Control
Flow control statements break up the normal flow of execution. Examples of this include for loops, if statements, do while, while loops, switch case, etc.
Difference between throw, throws, and Throwable
throw: Throws an exception throws: The method itself throws the exception Throwable: Class that encompasses errors and exceptions and allows us to create our own custom exceptions
Whats our signature/entry point?
public static void main(String[] args)
Overriding
Changing the logic of the method with the same name from a child class. You can't access the parent's method because the child deleted and replaced the parent's method
Scopes in Java
Static/Class: one copy of the variable and/or method Instance/Object: each instance has a copy of the variables and/or methods Method: variables that only exist within the method Block/Local: only exist within the block
Class
blueprint for objects
Autoboxing
Automatic conversion from primitive to reference types
Four Access Modifiers
public, private, protected, and default
Protected
The class, the current package, children
Default
The class and the current package
Array vs Arraylist
Array has a fixed size while Arraylist is dynamic
String Pool
Concept in Java that minimizes necessary for redundant strings. Its purpose is to be less memory intensive
JVM
Java Virtual Machine: Translates Java code so that the machine can read it
How to force the garbage collector?
You cannot force the garbage collector but you can suggest it by typing a System.gc();
Setters and Getters
Methods that retrieves private variables, associated with Encapsulation
What does the keyword "this" target?
The current instance Different ways to use: refer current class instance variables, invoke current class constructor, return the current class instance, as method parameter, invoke current class method, as an argument in the constructor call
Two Types of Polymorphism & Examples
Compiled: Polymorphism that can only be checked during runtime (overloading) Runtime: Polymorphism that can only be checked during runtime (overriding & type casting)
Unboxing
Automatic conversion from reference to primitive types
What is the minimum you need to run Java?
JRE
Wrapper Class
A class that wraps primitive types into reference objects
Instance/Object Scope
Each instance has a copy of the variable and/or methods
Difference between exception and error
Exception: An issue that arises in the code that interrupts the normal flow of the program (checked) Error: An issue that happens outside of the code (and outside the developers control) that interrupts the normal flow of the program (unchecked) Runtime: Exception thrown during runtime (unchecked)
Is Java pass by value or pass by reference?
Java is strictly pass by value.
Why Java?
Oracle upkeep, free, popularity, OOP, automatic garbage collector, based on C, rich API
Package
used to group similar classes and/or classes that work closely together to achieve some goal
Section 2
(22 cards)