A listener is an object that
a) implements any type of interfaceb) is used to accept any form of input
c) is an inner class to a class that has abstract methods
d) waits for some action from the user
e) uses the InputStreamReader class
Answer: d.
Explanation: The listener “listens” for a user action such as a mouse motion, a key entry or an activation of a GUI object (like a button) and then responds appropriately. Listeners allow us to write programs that interact with the user whenever the user performs an operation as opposed to merely seeking input from the user at pre-specified times.
Enhancing Classes
- 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?
- If the instruction z.set2(y.get1( )); is executed, 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