If the instruction z.set2(y.get1( )); is executed, which of the following is true?
a) (y = = z) is still trueb) (y.get1( ) = = z.get1( )) but (y.get2( ) != z.get2( ))
c) (y.get1( ) = = z.get1( )) and (y.get2( ) = = z.get2( )) but (y != z)
d) (y.get1( ) = = z.get2( )) and (y.get2( ) = = z.get1( )) but (y != z)
e) the statement causes a run-time error
Consider a class that stores 2 int values. These values can be assigned int values with the messages set1(x) and set2(x) where x is an int, and these values can be accessed through get1( ) and get2( ). Assume that y and z are two objects of this class. The following instructions are executed:
y.set1(5);
y.set2(6);
z.set1(3);
z.set2(y.get1( ));
y = z;
Answer: a.
Explanation: Since y=z; was performed previously, y and z are aliases, so that a change to one results in a change to the other. The statement z.set2(y.get1( )); is essentially the same as z.set2(z.get1( )); or y.set2(y.get1( )); and in any case, it sets the second value to equal the first for the object which is referenced by both y and z.
Enhancing Classes
- A listener is an object that
- JOptionPane is a class that provides GUI
- In order to have some code throw an exception, you would use which of the following reserved words?
- An exception can produce a “call stack trace” which lists
- A Java program can handle an exception in several different ways. Which of the following is not a way that a Java program could handle an exception?
- Assume that you are defining a class and you want to implement an ActionListener. You state addActionListener(this); in your class’ constructor. What does this mean?
- If s is a String, and s = “no”; is performed, then s
- Which of the following pieces of logic could be used in the method that implements Comparable? Assume that the method is passed Object a, which is really a ChessPiece. Also assume that ChessPiece has a method called returnType which returns the type of the given piece. Only one of these answers has correct logic.
- Which of the following method headers would properly define the method needed to make this class Comparable?
- In order to implement Comparable in a class, what method(s) must be defined in that class?
- Which of the following interfaces would be used to implement a class that represents a group (or collection) of objects?
- An object that refers to part of itself within its own methods can use which of the following reserved words to denote this relationship?
- If there are 4 objects of type StaticExample, how many different instances of x are there?
- What is the value of z after the third statement executes below?
- Static methods cannot
- Which of the following methods is a static method? The class in which the method is defined is given in parentheses following the method name.
- Consider the following swap method. If String x = "Hello" and String y = "Goodbye", then swap(x, y); results in which of the following?
- If the instructions z.set2(5); and y.set1(10); are performed, which of the following is true?
- The statement y.get2( ); will
- The statement z.get2( ); will
- If the operation y = x; is performed, then the result of (x = = y) is
- If the operation y = "Hello"; is performed, then the result of (x = = y) is
- The result of x.length( ) + y.length( ) is
- The result of (x = = y) is