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JAVA (EXAM 3) Questions & Answers
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All classes implement an abstract data type. - ANSWERFalse In a single statement, define and initialize a reference variable for an ArrayList named frameScores that stores items of type Integer. - ANSWERArrayList frameScores = new ArrayList(); Given: ArrayList itemsList = new ArrayList(); What is the initial size of the ArrayList? - ANSWER0; Zero The _________ operator is used to explicitly allocate an object. - ANSWERnew Given: Employee clerk1 = new Employee() ;. clerk1 refer to an object. - ANSWERTrue Define a private field named salary of type int for Employee class: - ANSWERprivate int salary; Which of the following commands is used to run a java program? - ANSWERjava The constructor has the same name as the class. The constructor method has no return type, not even void. - ANSWERTrue Class Dwelling has data members door1, door2, door3. A class House is derived from Dwelling and has data members wVal, xVal, yVal, zVal. The definition and initialization House h = new House(); creates how many data members? - ANSWER7; seven Using a JFormattedTextField variable named numItersField, write a statement that creates a JFormattedTextField that uses a NumberFormat to display integers. - ANSWERnumItersField = new JFormattedTextField(NumberFormat.getIntegerInstance()); The block tag specification below creates a reference to ElapsedTime's printTime() method. @see ElapsedTime#printTime() - ANSWERTrue
Given a JFrame variable named frame and a JTextField variable named nameField, write a statement that adds nameField to the frame. - ANSWERframe.add(nameField); Assume an empty JFrame object named appFrame. The program called the setVisible() method correctly (i.e., appFrame.setVisible(true);), but the frame is not visible on the screen. The frame should be 500 pixels wide and 300 pixels tall. - ANSWERappFrame.setSize(500, 300); Which of the following is NOT a characteristics of Object Oriented Programming? - ANSWERrevolution Using the GridBagConstraints variable named layoutConstraints, write a statement that would add 5 pixels of padding to the left and right of a GUI component. The top and bottom edges of the component should not have padding. - ANSWERlayoutConstraints.insets = new Insets(0, 5, 0, 5); Given the JTextField variable named weeklyHoursField, write a statement that makes weeklyHoursField editable by users. - ANSWERweeklyHoursField.setEditable(true); A private helper method may not call another private helper method. - ANSWERFalse Which access modifier allows a class be used by every class in the program regardless of the package in which either is defined? - ANSWERpublic Suppose your program uses an object called Student. Which of the following shall NOT be part of the Student object? - ANSWERgetPrice() By default, the equals() method tests the equality of the contents of two Objects , not the equality of their references. - ANSWERFalse Suppose that public Student(String name, String id){// code} is the only constructor the Student class has. Which of the following is correct? - ANSWERStudent s = new Student(â Tomâ , â 1234â ); A derived class may define a member method having the same name as the base class. Such a member method _______________ the method of the base class. - ANSWERoverrides Suppose that we have the following code. Student s1 = new Student(); Student s2; Which of the following is true after the above two line of code are executed? - ANSWERs1 refers to valid object
What is the output of the displayed code? Public class Test { public static void main( String args[]) { int intArray[] = new int [5]; .... for (int outerIndex = 1; outerIndex < intArray.length; ++outputIndex) { for (int innerIndex = 1; innerIndex < dbIArray.length; ++innerIndex) { dblArray [ innerIndex ] = innerIndx * outerIndex; } } for (int theIndex = 1; theIndex < dbLArray.length; ++theIndex) System.out.print( dbLArray[ theIndex } + ", "); } } - ANSWER4.0, 8.0, 12.0, 16.0, 20.0, 24.0, A key advantage of javadoc comments is that the documentation is close to the source code so is easier to keep consistent with the source code. - ANSWERTrue The while loop syntax is: while(condition); {//loop body statements} - ANSWERFalse Is the following code defines an enumeration type? public enum LightState {RED; GREEN; YELLOW; DONE} - ANSWERFalse Is this method correct for squaring an integer? public static int sqr(int a) { int t; t = a * a; return a;} - ANSWERFalse Which of the following is correct for loop structure? - ANSWERfor(int x = 1; x < 10; x++){}
If we rewrite for(int i = 1; i < 10; i++){//loop body} as a while loop. Which of the following is in loop body? - ANSWERi++; Each method call creates a new set of local variables, forming part of what is known as a _____________ - ANSWERstack frame Which of the following increase value of x by 1? Assume x is int type variable. - ANSWERx += 1; x = x + 1; x++; ++x; Each execution of the loop body is called an ___________ - ANSWERx != 0 !(x == 0) How many times the following while loop will be executed? Assume int x = 5; while(x > 0){ x--; } - ANSWER A local variable's scope extends from a method's opening brace to the method's closing brace. - ANSWERFalse Which correctly passes two integer arguments for the method call calcVal(...)? - ANSWER(99, 4+5) Suppose method void printAge(_________) has an int parameter userAge. Fill in the missing parameter. - ANSWERint userAge If a method's local variable has the same name as a field, the name will refer to the local variable. - ANSWERTrue
How many times the statement x++; executed? for(int i = 0; i < 9; i++);{ for(int j = 0; j < 9; j++); { x++;}}
- ANSWER The programmer must use special notation to pass an array by reference; otherwise an array is passed by value. - ANSWERFalse Suppose that int[] arr = new int[4]; has been initialized as 1, 2, 3, 4. What is the output of the following code? for(int i = 0; i < arr.length; i++) System.out.print(arr[i]); - ANSWER A return type of void indicates that a method does not return any value, in which case the return statement should simply be: ____________ - ANSWERreturn; When the program is run, what CD cost information will be displayed? - ANSWER8. For a method with three integer inputs, about 3-5 test vectors is likely sufficient for testing purposes.
- ANSWERFalse Define and initialize a two dimensional array of integers named dataVals with 4 rows and 7 columns using default element values. - ANSWERint[][] dataVals=new int[4][7]; To Avoid writing redundant code is one of the reasons that we write method - ANSWERfalse A FIXME comment is commonly used to indicate program parts to be fixed or added. - ANSWERTrue Write a statement that converts the text representation of an integer within String numberText, storing the value in an int variable numLanes. - ANSWERnumLanes = Integer.parseInt(numberText);
Which access modifier allows a class only be used by self? - ANSWERprivate A private helper method may not call another private helper method. - ANSWERFalse Given the JButton variable named convertButton, write a statement that adds an ActionListener to convertButton. Use the "this" keyword. - ANSWERconvertButton.addActionListener(this); Given the JLabel variable named nameField, write a statement that creates a JLabel with the text "Name:". - ANSWERnameField = new JLabel("Name:"); Which of the following is NOT a characteristics of Object Oriented Programming? - ANSWERrevolution Assume an empty JFrame object named appFrame. The program called the setVisible() method correctly (i.e., appFrame.setVisible(true);), but the frame is not visible on the screen. The frame should be 500 pixels wide and 300 pixels tall. - ANSWERappFrame.setSize(500,300); Write a statement that sets the text of a JTextField component named nameField to "Mary". - ANSWERnameField.setText("Mary"); The block tag specification below creates a reference to ElapsedTime's printTime() method. @see ElapsedTime#printTime() - ANSWERTrue Write a single statement that gets the value of a JFormattedTextField called speedField as a double and stores it in a variable of type double called carSpeed. - ANSWERcarSpeed = ((Number)speedField.getValue()).doubleValue(); Programmers commonly draw class inheritance relationships using UML notation. What UML stands for? - ANSWERUnified Modeling Language A programmer must provide at least a default constructor. Otherwise, the class will have no constructors. - ANSWERFalse
Which of the following is not javadoc tags? - ANSWER@argument The loop body of a do-while loop will be executed at least once - ANSWERTrue enum type definition occurs inside the method. - ANSWERFalse Returning the incorrect variable from a method is a common error. - ANSWERTrue Which of the following is correct for loop structure? - ANSWERfor(int x = 1; x < 10; x++){} every while loop can be rewrite as a for loop - ANSWERFalse A return address indicates the value returned by the method. - ANSWERFalse Which of the following decrease value of x by 1? Assume x is int type variable. - ANSWERx -= 1; x = x - 1; x--; In a while loop, once execution enters the loop body, execution continues to the body's end even if the loop condition expression becomes false midway through. - ANSWERTrue Write loop condition: x and y are not both zero. - ANSWERx != 0 || y != 0 !(x == 0 && y == 0) How many times the following while loop will be executed? Assume int x = 5; while(x >= 0){ x--; } - ANSWER
A return type of void indicates that a method does not return any value, in which case the return statement should simply be: ______________. - ANSWERreturn; Given a method definition: void calcVal(int a, int b, int c) and given int variables i, j, and k, which are valid arguments in the call calcVal(...)? - ANSWER(i+5, j+6, k+10) void myMthd(int userNum + 5) is a valid method head. - ANSWERFalse A local variable's scope extends from a method's opening brace to the method's closing brace. - ANSWERFalse In Java, what is the most efficient way to store and randomly access a sequence of objects? - ANSWERarray How many times the statement x++; executed? for(int i = 0; i < 9; i++);{ for(int j = 0; j < 9; j++) { x++;}}
- ANSWER In contrast to primitive types, a method parameter of array (or object) type is pass by ____________.
- ANSWERreference Suppose that int[] arr = new int[4]; has been initialized as 1, 2, 3, 4. What is the output of the following code? for(int i = 1; i < arr.length; i++) System.out.print(arr[i]); - ANSWER Given: void printSomething (int num1) { ... }. Then return 0; a valid return statement. - ANSWERFalse What is the best routine to interchange the values stored in location1 and location2? - ANSWERtemp = location2; location2 = location1; location1 = temp; For a method with three integer inputs, about 3-5 test vectors is likely sufficient for testing purposes.
- ANSWERFalse
The block tag specification below creates a reference to ElapsedTime's printTime() method. @see ElapsedTime#printTime() - ANSWERTrue Given a JFrame variable named frame and a JTextField variable named nameField, write a statement that adds nameField to the frame. - ANSWERframe.add(nameField); Assume an empty JFrame object named appFrame. The program called the setVisible() method correctly (i.e., appFrame.setVisible(true);), but the frame is not visible on the screen. The frame should be 500 pixels wide and 300 pixels tall. - ANSWERappFrame.setSize(500, 300); The JVM automatically performs runtime polymorphism to determine the correct method to call. - ANSWERTrue Using the GridBagConstraints variable named layoutConstraints, write a statement that would add 5 pixels of padding to the left and right of a GUI component. The top and bottom edges of the component should not have padding. - ANSWERlayoutConstraints.insets = new Insets(0, 5, 0, 5); Given the JTextField variable named weeklyHoursField, write a statement that adds an ActionListener to weeklyHoursField. Use the "this" keyword. - ANSWERweeklyHoursField.addActionListener(this); A public member method may not call another public member method. - ANSWERFalse Which access modifier allows a class be used only in other classes within the same package, i.e. known as package private? - ANSWERno specifier Suppose your program uses an object called Student. Which of the following shall NOT be part of the Student object? - ANSWERgetPrice() All classes can access Object's public and protected methods (e.g., toString() and equals()) even if such methods are not explicitly overridden. - ANSWERTrue Suppose that public ShoppingItem(double price, int quantity) is the only constructor the ShoppingItem class has. Which of the following is correct? - ANSWERShoppingItem item = new hoppingItem(3.85, 5);
Suppose that we have the following code. Student s1 = new Student(); Student s2 = s1; Which of the following is true after the above two line of code are executed? - ANSWERs1 and s2 both refer to valid objects Assigning a different value to a reference parameter within the method deletes the original object. - ANSWERFalse A ____________ method may modify the class fields. - ANSWERmutator If every line of code was executed at least once (complete code coverage) and all tests passed, the class must be bug free. - ANSWERFalse Within a member method, the implicitly-passed object reference is accessible via the keyword ____________. - ANSWERthis Suppose that Team class has an object of Person class as attribute. True or False: Person class uses Team class. - ANSWERFalse Define a variable called gameScore that refers to a primitive wrapper object with an int value of 81. Use the object initialization style. - ANSWERInteger gameScore = new Integer(81); Write a statement that assigns the int representation of the value held by the Integer objects totalPins to a primitive int variable pinScore. - ANSWERpinScore = totalPins.intValue(); Each item in array is directly accessible. - ANSWERTrue Given array firstList with size 4 and element values, 33, 44, 55, 66, and array secondList with size 4 and elements values 0, 0, 0, 0. firstList = secondList; copies 0s into each firstList element. - ANSWERFalse What is contained in each element of the array when the following statements are executed? int numbers[]; numbers = new int[2]; - ANSWER
How many times the following while loop will be executed? Assume int x = 5; while(x != 0){ x -= 2; } - ANSWERinfinite times A ______________ is a list of statements surrounded by braces. - ANSWERblock Given a method definition: void calcVal(int a, int b, int c) what value is assigned to b during this method call: calcVal(42, 55, 77); - ANSWER Call a method void printAge(int x), passing the value 21 as an argument. - ANSWERprintAge(21); If a method's local variable has the same name as a method parameter, the name will refer to the local variable - ANSWERFalse Which of the following correctly shows the syntax for accessing the value in an array element? - ANSWERarray-identifier[int-index-value]; How many times the statement x++; executed? for(int i = 0; i < 9; i++);{ for(int j = 0; j < 9; j++); { x++;}}
- ANSWER The programmer must use special notation to pass an array by reference; otherwise an array is passed by value. - ANSWERFalse Suppose that int[] arr = new int[4]; has been initialized as 1, 2, 3, 4. What is the output of the following code? for(int i = 0; i < arr.length; i++) System.out.print(arr[i]); - ANSWER A return type of _________ indicates that a method does not return any value, in which case the return statement should simply be: return; - ANSWERvoid Which song is printed to the screen last? - ANSWERShake It Up and Go A good programmer takes the time to test all possible input values for a method. - ANSWERFalse How many total integers elements are in an array with 4 rows and 7 columns? - ANSWER
what are the reasons for writing methods? - ANSWERImprove program readability Modular program development Avoid writing redundant code A good programming process is to write the entire program, then incrementally remove bugs one at a time. - ANSWERFalse Assume that int[] a = now int [9]; Write one line of code to assign the first element in array ro be 100.
- ANSWERa[0] = 100; Given array firstList with size 4 and element values 33, 44, 55, 66 and array secondList with size 4 and elements values 0,0,0,0, firstList = secondList; copies 0s into each firstList element. - ANSWERFalse What is the index of the last element in an array? - ANSWERThe size of the array minus one A break statement in a loop causes an immediate exit of the loop - ANSWERTrue What is the output of the program? - ANSWERAn IndexOutOfBoundsException occurs during runtime A key advantage of javadoc comments is that a change to a comment in the java source automatically updates documentation on an HTML webpage - ANSWERTrue The do-while loop syntax is: do{//loop body statements } while(condition) - ANSWERFalse In many situation, an eumeration is clearer, requires less codes, and is less prone to error - ANSWERTrue Is this method correct for squaring an integer? public static int sqr(int a) {int t; t = a* a;} - ANSWERFalse Which of the following is correct for loop structure - ANSWERfor(int x = 1; x <10; x++){}
How many times the inner loop body executed? for(int i = 0; i < 9; j++) { x++;}} - ANSWER The programmer must use special notation to pass an array by reference; otherwise an array is passed by value. - ANSWERFalse Suppose that int[] arr = new int[4]; has been initialized as 1,2,3,4. What is the output of the following code? for(int i = 0, i < arr.length, i++) System.out.print(arr[i]); - ANSWER A return type of void indicates that a method does not return any value, in which case the return statement should simply be ________________. - ANSWERreturn; For method, border cases might include 0, a very large negative number, and a very large positive number. - ANSWERTrue How many elements are in the array defined as: char[][] streetName = new char[20][50]; - ANSWER To Avoid writing redundant code is one of the reasons that we write method - ANSWERFalse Experienced programmers develop programs incrementally, meaning they create a simple program version, and then growing the program little-by-little into successively more-complete versions. - ANSWERTrue An ADT's interface is defined by the ADT's public member method declarations. - ANSWERTrue Assign the Integer element at index 8 of integer ArrayList frameScores to an Integer variable currFrame. - ANSWERcurrFrame = frameScores get(8); Given ArrayList itemsList = new ArrayList(); After itemsList set(0,99);, what is the ArrayList's size? - ANSWERthe code has error The ______________ construct defines a new type that can group data and methods to form an obejct - ANSWERclass
The programmer defines each field after the ________ access modifier, making clear that a class user cannot directly access the fields. - ANSWERprivate Define a private field named salary of type int for Employee class, - ANSWERprivate int salary; Write a command using the Java compiler to compile a program consisting of classes Ingredient, Recipe, and FamilyCookbook. Preserve this class ordering. - ANSWERjavac Ingredient.java Recipe.java FamilyCookbook.java The constructor has the same name as the class. The constructor method has return type void. - ANSWERFalse Class Dwelling has data members door1, door2. door3. A class House is derived from Dwelling and has data members wVal, xVal, yVal, zVal. The definition and initializa - ANSWER Write a single statement that gets the value of a JFormattedTextField called speedField as a double and stores it in a variable of type double called carSpeed. - ANSWERcarSpped = ((Number)speedField.getValue()).doubleValue(); The @author block tag can be used to specify a method's author. - ANSWERFalse Write a statement that sets the text of a JTextField component named nameField to "Mary". - ANSWERnameField.setText("Mary"); Assume an empty JFrame object named appFrame. - ANSWERappFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); The relationship between House and Window is: Has-a-relationship. - ANSWERTrue Given the JLabel variable named nameField, write a statement that creates a JLabel with the text "Name". - ANSWERnameField = new JLabel("Name: "); Given the JTextField variable named weeklyHoursField, write statement that makes weeklyHoursField editable by users. - ANSWERweeklyHoursField.setEditable(true);
