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What's a syntax error?
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Section 1
(50 cards)
What's a syntax error?
When any programming statements violate the syntax rules of the Java language; ex. [System.out.println("There is a mistake here.)]- the error is the missing " and ;
What value is computed by the following Java expression? 10 / 3 - 14 % 2
3 (14 % 2 = 0 and 10/3 = 3.3 but there's no double value so round to the lowest integer
If gen is a Random object, what range of values would the following expression produce? gen.nextInt(70) - 20
-20 to 49
String is a Java primitive type. True False
False
A String literal cannot span multiple lines in a Java program. True False
True; Opening and closing quote must be on the same line of code so to print multiple lines you concatenate the lines
What does the || boolean operator mean and what does X || Y give?
|| means Or; X || Y will be true if X or Y or BOTH are true and false otherwise
In Java, object reference variables do not have to be declared. True False
False
What output would be produced by the following statement? System.out.print("ABC" + 10 + 5);
ABC105
Which of the following identifiers follows the Java convention for a variable name? Max_Height MAX_HEIGHT MaxHeight maxHeight
maxHeight
What value is stored in the variable x after the following code segment is executed? int x = 0; for (int i = 1; i <= 4; i++) x = x + i;
10
What's a software development environment? The software that lets you develop Java programs. The library of Java classes that any programmer can use. A conceptual platform on which Java programs run. The software that checks and translates Java code
The software that lets you develop Java programs; set of tools used to create, organize, modify, test, and debug a program; ex. BlueJ
What value is computed by the following Java expression? 6 + 2 * 3 - 3
9
What are the two types of software development environment and what are they?
1) Command-line environment- console/terminal window that prompts you to enter text commands; JDK is set of command-line tools 2) Integrated development environments (IDE's)- tools are integrated into one program that provides a graphical user interface (Eclipse or BlueJ)
What output would be produced by the following code? String text = "idiosyncratic"; System.out.print(text.substring(2, 7));
iosyn
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.substring(9, 12) give?
not substring with two values gives back from index of the first value to the index of the second value - 1
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.charAt(0) give?
T charAt gives the character it's asked for in a specific index number
What does the ^ boolean operator mean and what does X ^ Y give?
^ means Exclusive Or; X ^ Y will be true if X or Y (but not both) are true and false otherwise
If gen is a Random object, what range of values would the following expression produce? gen.nextInt(100)
0 to 99 Remember: When there's one number, it ranges from 0 to N-1; but if have a shift value of Y, it will be from Y to N+Y-1
Which of the following is NOT a feature of the Java programming language? It is graphics neutral. It is platform independent. It has automatic garbage collection. It is an object-oriented language.
It is graphics neutral; IT IS general-purpose, has applets to be able to run on web tech, & it was created by Sun and is now ran by Oracle
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.replace("be", "are") give?
To are or not to are replace replaces the first word or character with the second word or character
If A is true and B is false, what is the value of the expression A && B? True False
False
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.concat("xyz") give?
To be or not to bexyz concat adds whatever characters to the string
The functionality of a for loop can always be written as a while loop. True False
True
What does the ! boolean operator mean and what does !X give?
! means Not; !X will be true if X is false and false if X is true; also called a unary operator bc it only requires one operand
What are the 8 primitive data types?
Byte, short, int, long (integers); float, double (floating-point types); char (character type); boolean (boolean type)
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.indexOf("r") and str.indexOf("or") give?
7 and 6 indexOf gives back index value of first occurrence of the value or word given
The compiler will issue an error if you violate a Java programming convention. True False
False; Conventions are rules outside of the language syntax that programmers should follow; ex. indentation, comments, spaces, etc
What is the boolean primitive type boolean?
Represents true or false
What is the Java API? The software that lets you develop Java programs. The library of Java classes that any programmer can use. A conceptual platform on which Java programs run. The software that checks and translates Java code
A large library of Java classes that any programmer can use; organized into packages and classes from the API can be imported
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.length() give?
18 Length is the number of characters so last index + 1
Are numeric types signed? True False
True
If gen is a Random object, what range of values would the following expression produce? gen.nextInt(50) + 20
20 to 69
Computing an incorrect result is an example of what kind of error? Production error Logic error Runtime error Syntax error
Logic error
What is the value of num after the following code segment is executed? int num = 12; num *= 3; int val = num + 1; num = num + val;
73
Given the following code segment: for (int i = 1; i < 10; i++) { System.out.println("apple"); for (int j = 1; j <= 5; j++) System.out.println("lemon"); } How many times does the word "apple" get printed? How many times does the word "lemon" get printed?
9, 45
Which expression can be used to determine if num is an even number? (even) num num / 2 != 0 Math.even(num) num % 2 == 0
num % 2 == 0
What is the difference between the floating-point types float and double?
Both hold values w/ decimals but float values includes the F character
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.substring(9) give?
not to be substring with just one value gives back from index of that value to the end of the string
What's a runtime error?
When any program executes and causes it to terminate abnormally; "crashes" or "blows up"; ex. when try to divide a # by zero, [123/0]
What is the character primitive type char?
Represents a single character
What is the difference between the integer primitive data types int, long, short, and byte?
int-stores an integer but not as large as long long- stores a large integer (includes L character) short- stores a shorter integer than int byte- stories the shortest amount of integers
If A and B are both true, what is the value of the expression A || B? True False
True
A Java compiler translates Java byte code into source code. True False
False; the compiler translates source code (code you write) into byte code
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.equals("xyz") give?
False equals checks if str has the same characters as inputed, if not, false, if does, true
What do the
and \t characters do?
starts a new line in a string and \t makes a tab
What value is computed by the following Java expression? 10 % 4 * 10 + 10
30
What is an escape sequence?
A technique for representing a character in situations where the traditional manner would cause problems or be less convenient; begins with the backslash (\) ex. [System.out.println("\"Tell the truth and then run.\"");
Assume the variable str refers to a string object containing the characters "To be or not to be" What does str.toLowerCase() and str.toUpperCase give?
Just changes the str either to all lower case or all upper case
What does the && boolean operator mean and what does X && Y give?
&& means And; X && Y will be true if both X and Y are true and false otherwise
What is the Java Virtual Machine (JVM)? The software that lets you develop Java programs. The library of Java classes that any programmer can use. A conceptual platform on which Java programs run. The software that checks and translates Java code.
A conceptual platform on which bytecode is designed to run on Java programs (makes Java platform-independent-meaning it can run on any computer with the JVM)
Section 2
(50 cards)
Code indentation is ignored by the compiler (T or F)
True
What is the value of val after the following code segment is executed int val = 20; val *= 2; val = val + 5;
45
The state of an object is represented by what? The values of its instance data. The visibility modifiers used on its instance data. The methods in its public interface. The signatures of its methods.
The values of its instance data.
Given the following code, which of the expressions is false? Point p1 = new Point(8, 12); Point p2 = new Point(8, 12); Point p3 = p2; p2.equals(p1) p1 == p2 p2 == p3 p3.equals(p1)
p1 == p2
A for-each loop can always be translated into an equivalent for loop. True False
True
What is the value of the following expressions? 12 / 5 + 12 % 5
4
The JavaFX graphics framework is designed to replace older technologies such as Swing and AWT. True False
True
Debugging is the process of evaluating a program to discover errors (T or F)
False, testing means this. Debugging is the process of determining the root cause of a problem and fixing it
The Java API is organized into what? A) Packages B) Groups C) Tuples D) Objects
A) Packages
What is the value of the following expressions? 2 + 2 / 4 + 6
8
Where is the origin point on a Java container (such as a Pane)? The center of the visible space The upper right corner The upper left corner The center of the container's original size
The upper left corner
The ASCII character set is a subset of the Unicode character set (T or F)
True
A for-each loop cannot be used to store values in an array. True False
True
A JavaFX Arc is defined as a portion of what other shape? Circle Polyline Line Ellipse
Ellipse
Which of the following is NOT true about the this reference? It can be used to call a method from another class. It can be used to call a constructor. It can be used to explicitly refer to the object on which a method is called. It can be used to distinguish a parameter from instance data.
It can be used to call a method from another class
A constructor cannot be overloaded. True False
False
In Java, an array is an object. True False
True; it is NOT a primitive type
A getter method always returns an integer value. True False
False
What value is printed by the following code? int[] myStuff = new int[400]; System.out.println(myStuff.length);
400
A method that does not return a value should have a return type of void (T or F)
True
What happens when an invalid index is used to access an array? The closest valid index is used. An exception is thrown. The statement is ignored. The compiler will issue an error message.
An exception is thrown
In a JavaFX Polygon object, the last vertex point is automatically connected to the first. True False
True
Each object has its own memory space for instance data (T or F)
True
If a binary search is used to find the value 74 in the following list of numbers, how many comparisons will it take? 12 19 23 28 35 37 40 49 54 61 65 74 82 88 93
2
Approximately what percentage of the viable candidates does a binary search algorithm eliminate with each comparison?
50
When viewed as as a black box, an object presents the client with which of the following? Its public interface Its prime sieve Its object signature Its command-line arguments
Its public interface
Given the following declaration, which expression will extract the substring "show"? String phrase = "I could show you incredible things";
phrase.substring(8, 12)
How many assignment statements are needed to swap two elements in an array?
3
When comparing String objects, on what does the compareTo method base its result? Character positions in the Unicode character set Demographic order String numeric values after non-alpha characters are removed Alphabetical order
Character positions in the Unicode character set
Which expression determines whether x is an odd number? A) x / 2 != 0 B) Math.odd(x) C) x % 2 == 1 D) (odd)x
C) x % 2 == 1
What does the following code accomplish? int x = sizes[0]; for (int val : sizes) if (val < x) x = val; Determines the maximum value in the array sizes Determines the minimum value in the array sizes Computes the sum of the values in the array sizes Performs a linear search on the array sizes
Determines the minimum value in the array sizes; it would be determining max value if it the 3rd line was [if (val > x)]
JavaFX embraces which of the following? A theater analogy A museum analogy A printing press analogy A portrait analogy
A theater analogy
Suppose a method called checkPos was to return true if both of its parameters was positive, and false otherwise public ____ checkPos (int a, int b) { return _____; } What would go in the first and second blank respectfully?
Boolean, a > 0 && b > 0
A Java compiler translates Java source code into bytecode (T or F)
True
BlueJ is an integrated development environment (IDE) (T or F)
True
If a method doesn't return a value, what should its return type be? There should be no return type. void this null
Void
The return type of a constructor must be void (T or F)
False
If an instantiation list is used to create an array, the new operator is not used. True False
True
Which of the following violates the principle of encapsulation? public constants private methods public methods public instance data
Public instance data
Variables declared within a method cease to exist when the method returns control to the caller. True False
True
What is the range of the valid indexes for an array that can hold 300 values?
0 to 299
Which analogy is appropriate? A) a class is like a car and an object is like a truck B) an object is like a car and a class like a truck C)a class is like a blueprint and an object is like a house D) an object is like a blueprint and a class is like a house
C)a class is like a blueprint and an object is like a house
Scaling a JavaFX Group object causes each element in the group to be scaled by the same amount. True False
True
Within a class, methods must have unique names. True False
False; can have same name just have different parameter lists; called method overloading
Logic errors are caught by the compiler (T or F)
False
Given the following code segment int num = 0, val = 1; while (val < 8) { val = val + 2; num = num + val; } What number is stored in the variable val after the loop ends? What number is stored in the variable num after the loop ends?
9, 24
All methods of a class can access data declared at the class level (T or F)
True
What is the value of the following expressions? 7 + 3 * 2 - 1
12
Which of the following is the proper way to set up an object to read from an input file? PrintWriter in = new PrintWriter("myInput.txt"); Scanner in = new File("myInput.txt"); File in = new File(new Scanner("myInput.txt")); Scanner in = new Scanner(new File("myInput.txt"));
Scanner in = new Scanner(new File("myInput.txt"));
The element type of an array can be any type except boolean. True False
False
Section 3
(50 cards)
T/F: The Java keyword this is an explicit reference to the object on which a method is invoked.
True, this allows an object to refer to itself in methods declared inside that object.
T/F: Both dimensions of a two-dimensional array must have the same element type
True
Which of the following is NOT true about the this reference? A) it can be used to call a constructor B) it can be used to call a method from a parent class C) it can be used to distinguish a parameter from instance data D) it can be used to explicitly refer to the object on which a method is invoked
B) it can be used to call a method from a parent class
The minimum number of value is minimized to 1 and the maximum value is equal to the number of sides. What is the output of the following code? Die die = new Die(20); die.roll(); die.roll(); System.out.println(die.getValue());
A number between 1 and 20
Encapsulation ensures which of the following? A) that hackers cannot breach the data in an object B) that a class cannot be used to derive another class C) that a client is the same class as the object with which it communicates D) that an object is in charge of modifying the values of its data
D) that an object is in charge of modifying the values of its data
T/F: Encapsulation makes is difficult for hackers to access your data.
False, Encapsulation is not about guarding against security breeches.
If the compiler finds two or more methods that equally match a given call, it will issue an error. This problem is called a(n)
ambiguous invocation
T/F: The deposit method of the BankAccount class is a mutator method
True
T/F: Two methods in the same class can have the same name
True
Assuming list is an array, what does the following for-each loop accomplish? A) nothing- the values in the array list are unchanged B) all elements in the array are set to 10 C) only the last element in the array is set to 10 D) only the first element in the array is set to 10
A) nothing- the values in the array list are unchanged; a for-each loop CANNOT change the values of the array
T/F: You cannot use relational operators (such as < or >) on objects.
True, You have to use the compareTo method instead.
T/F: A class must have a getter and setter method for each instance variable.
False, They sometimes do, but don't have to.
Caused when you try to access an array element that doesn't exist.
Bounds error
T/F: Constructors cannot be overloaded.
False, Sure they can, and often are. Overloaded constructors provide different ways to set up an object.
The elements of an array of length N can be accessed using what range of indexes?
0 to N-1
T/F: The behavior of an object is determined by its public interface
True
What is the method signature of the method below? public void setCoordinates(int x, int y)
setCoordinates(int, int) Remember, method signatures (and parameters) MUST BE UNIQUE for method overload to be acceptable
Method overloading is helpful in which of the following situations? A) When two methods have different return types B) When a method has the same name as its enclosing class. C) When two methods perform a similar task on different types of data. D) When two classes have the same name E) When two methods perform a different task on the same types of data.
C) When two methods perform a similar task on different types of data.
T/F: A method can only be an accessor or a mutator but not both.
False, It can be both, such as a method that changes an instance value and then returns the new value.
T/F: Traversing an array or collection means accessing each element one at a time.
True, common for for-each loop
T/F: If you call a method through a null reference the compiler will issue an error
False; null just means that nothing's there or that whatever value is not there
A one-dimensional array has only one element type, but a multidimensional array can hold several types of elements. True False
False; Every array has a single element type. The difference is in how the values are arranged.
An integer value that is used to access a particular element in an array.
Index
T/F: Arrays can hold primitive types, but not objects.
False, The element type of an array can be either a primitive type or an object reference.
Given the following code segment: int list[] = new list[10]; for (int i = 0; i < list.length; i++) list[i] = i * 10; What is the value of list.length?
10
What violates encapsulation?
Public variables and instance data
The minimum number of value is minimized to 1 and the maximum value is equal to the number of sides. What is the output of the following code? Die die = new Die(6); System.out.println("Die value: " + die);
Die value: 1
An ellipses (...) is used to specify a method that accepts command-line arguments. True False
False; a variable-length parameter is specified using an ellipses (..) between the type and parameter name
T/F: Getter methods always return a String.
False, The return type of each getter method must match the type of the value being retrieved.
When performing a binary search, how many comparisons are required to find a value in a list of N values, in the worst case?
log2N + 1
T/F: The return type of a method is NOT part of the method's signature
True
How many comparisons are necessary to find the value 43 in the following list using a binary search? 13 25 28 30 39 43 44 58 66 70 78 81 86 88 95
3
What doesn't violate encapsulation?
Private variables/instance data, public methods, private methods, constants
The println method accepts a variable number of parameters.
False
Given the following code segment: int list[] = new list[10]; for (int i = 0; i < list.length; i++) list[i] = i * 10; What is the value of the last element in the list array after this code completes?
90
T/F: An array that holds objects cannot be created using initialization lists
False
T/F: The main method accepts a variable-length argument list
False; main method accepts an array of String objects as a parameter called args which represents any command-line arguments that are provided when the program is run
What does the this reference refer to? A) the object on which a method is invoked B) the object passed as the first parameter to a method C) the object returned by a method D) the parent object of the current object
A) the object on which a method is invoked
The main method accepts an array of String as a parameter. True False
True
A two-dimensional array is suitable for storing tabular data. True False
True; The two dimensions of the array mimic the row and column layout of the table.
What is part of the method signature?
name of the method and the type of its parameters; all method signatures must be unique
T/F: The toString method is automatically called when an object is printed.
True, And when an object is concatenated with a string; but the toString method DOES NOT print anything
T/F: A binary search only works on a list of sorted elements
True
Program options are often specified using what?
Command-line arguments
T/F: A bounds error will result in an exception being thrown
True; like when an invalid index is used to access an array
Given the following code segment: int list[] = new list[10]; for (int i = 0; i < list.length; i++) list[i] = i * 10; What is the value of the first element in the list array after this code completes?
0
An object that holds a set of values that can be accessed using a numeric index.
Array
Which method signature could NOT represent an overloaded version of the following method? public int max(int x, int y) { return (x > y) ? x : y; } A) max(Object, Object) B) max(int, int) C) max(double, double) D) max(String, String) E) max(int, int, int)
B) max(int, int) bc the signatures match exactly so this couldn't be an overloaded version of the method.
T/F: The element type of an array can be any type except boolen
False
Given the following code segment: int list[] = new list[10]; for (int i = 0; i < list.length; i++) list[i] = i * 10; What is the value of list[3] after this code completes?
30
Section 4
(50 cards)
What must the child of an abstract class provide in order not to be considered abstract also?
Must provide definitions for the inherited abstract methods
Deriving one class from another establishes what kind of relationship between the two classes?
is-a
What is dynamic binding?
When a line of code calls the same method every time and Java defers this binding until run time; ensures that the invocation is polymorphic
A two-dimensional array is really a one-dimensional array of one-dimensional arrays. True False
True; Each dimension of a multidimensional array is really a single-dimensional array.
The maximum indexes of a two-dimensional array with 6 rows and 10 columns are 5 and 9, respectively. True False
True; Each dimension is indexed from 0 to N-1, where N represents the number of elements in that dimension.
What's different about an overridden method in a subclass compared to the inherited version? different parameters but same method name and code same method name and parameters but different code different method name but the same code same method name and code but different return type
same method name and parameters but different code
The instanceof operator determines if an object reference variable is currently pointing to an object of a particular type. True False
True; It produces a boolean (true or false) result.
What is the ultimate root of every class hierarchy?
java.lang.Object class
What are abstract methods?
methods headers with no bodies
Which of the following identifiers follow the naming convention for a Java constant? maxPenalties MAX_PENALTIES MAXPENALTIES Max_Penalties
MAX_PENALTIES
The expression x^y raises the value x to the power y. True/False
False; Use Math.pow(x, y) instead
What is the difference between method overloading and overriding
Method overloading is when two or more Java methods in the same class have the same name but as long as have different parameters; Overriding is when a method from the parent class is defined again in the sub class (overriding the inherited version) with own version
How does the default version of the equals method act if not overridden?
Acts as the == operator, so returns true if two references point to the same object
When is an abstract class useful?
When it is used to derive other classes; to make a class abstract must use abstract in the class header
What can an object reference variable refer/point to?
Any object of it's type or any type derived from it ex. A car reference could point to a car object or sedan or suv object but NOT vice-versa Car automobile; automobile = new Car(); automobile = new Sedan(); automobile = new SUV();
If the final modifier is applied to a class, that class cannot be used to derive a subclass True/False
True
Which line of code demonstrates a valid and error-free way to access the following array? String[][] chessboard = new String[8][8]; String chessPiece = chessboard[1][8]; String chessPiece = chessboard[1]; String chessPiece = chessboard["2"]["3"]; String chessPiece = chessboard[5][2]; String chessPiece = chessboard[4][];
String chessPiece = chessboard[5][2]; it's within the bounds and correctly called
The first parameter to the printf method is the format string. True/False
True; It determines what the output will look like. Ex. System.out.printf("|%-10d|%n", num); // width of 10, left justified
Method overloading is helpful in which of the following situations? When two classes have the same name. When two methods have different return types. When a method has the same name as its enclosing class. When two methods perform a similar task on different types of data. When two methods perform a different task on the same types of data
When two methods perform a similar task on different types of data.
What Java keyword is used to create a subclass? interface implements extends inherits
Extends
A Java interface defines which of the following? system interface keyword interface printable interface user interface
system interface; It defines the way one part of a system can talk to another.
Graphically and in code, from what to what do you read the is-a relationship ?
Graphically: from the start of arrow to end of arrow In code: From right to left ex. Vehicle v; v= new Sedan(); A sedan IS A vehicle but a vehicle isn't always a sedan
What's an abstract class?
is a placeholder in a class hierarchy that represents a general concept
An integer can equal a double True/False
False; only a double can equal an integer
What are synonyms for the new class, the subclass?
Child class, derived class
Every class can only have one parent. True/False
True; called single inheritance; a parent can derive multiple classes though
What's a polymorphic reference?
object variable that can refer to different types of objects at different points in time
If Lockable is an interface, which statement must be true given the following declaration? Lockable obj = new Book(); Lockable must define the methods in Book Book must contain Lockable Book must implement Lockable Lockable must implement the Book class
Book must implement Lockable
A Java interface cannot be instantiated. True False
True; unlike a class, you cannot create an object from an interface just methods
What does the % sign perform?
The remainder, so how much there is leftover AFTER the division is performed
Assuming the table is a two-dimensional array of integers, what does the following code do? int sum = 0; for (int i = 0; i < table.length; i++) for (int j = 0; j < table[i].length; j++) sum = sum + table[i][j]; Computes the sum of each column in the table. Computes the sum of all elements in the table except those in the last column. Computes the sum of all elements in the table except those in the last row. Computes the sum of each row in the table. Computes the sum of all values in the table.
Computes the sum of all values in the table.
An abstract can only contain abstract methods True/False
False; it can also contain fully defined methods
If a class is not explicitly derived from a particular class, where is it derived from?
The Object class; can therefore point to any object bc it's inherited by all classes
When a method is invoked, what determines which is invoked?
The type of the object NOT the type of reference
What character set does Java use to represent characters?
Unicode
How many elements can be stored in a two-dimensional array with dimensions 5 and 10?
50
An abstract class can instantiated True/False
False
A class can only implement one interface at a time. True False
False; a class can implement multiple interfaces
If both operands to the remainder operator (%) are positive, a divisor of n will produce a result in the range 1 to n. True/False
False; It will produce a result in the range 0 to n-1.
It is possible to create an array with more than two dimensions. True False
True; A multidimensional array can have any number of dimensions, though more than three dimensions is rare.
What is polymorphism?
is the ability of a language to determine at runtime which of several possible methods will be executed
If the final modifier is applied to a method, that method cannot be overridden in any derived class True/False
True
Which of the following statements is true? An interface can contain public and private methods. An interface can contain methods and classes. An interface can contain methods and constants. An interface can contain methods and instance variables.
An interface can contain methods and constants.
The methods of the Math class are called through the class name because they are abstract. True/False
False, the methods of the Math class are static
An abstract class cannot be declared as final
True bc it must derive classes from it since it's abstract
The methods in a Java interface are abstract. True False
True; Interface methods don't have a body defined for them. That's up to the class that implements the interface.
Private data and methods cannot be accessed by name in a derived class True/False
True
What are synonyms for the existing class, the superclass?
Parent class, base class
How can it be determined what type of objects an object reference can refer to?
Distinguish between the object reference type and the type of object (class) it refers to
Methods and data declared as protected can be accessed from any derived class True/False
True
Section 5
(47 cards)