Analyze the following code:
import java.util.StringTokenizer;
public class A extends StringTokenizer {
}
B. The program has a compilation error because the default constructor of A invokes the default constructor of StringTokenizer, but StringTokenizer does not have a default constructor.
C. The program would compile fine if you add the following constructor into A: A(String s) { }
D. The program would compile fine if you add the following constructor into A: A(String s) { super(s); }
The correct answer is BD
Explanation: StringTokenizer has three constructors StringTokenizer(String s), StringTokenizer(String s, String delimiters), and StringTokenizer(String s, String delimiters, Boolean returnTokens). It does not have a default constructor. If a class does not specify a constructor, a default constructor is assumed. A constructor invokes its superclass?s default constructor if it does not explicitly invoke a constructor.
Java
- In Java, the mechanism that allows you to combine data and operations on the data into a single unit is called a(n)
- Which of the following is a legal way to declare and instantiate an array of 10 Strings?
- The statement System.out.println(values[7]); will
- Which of the following loops would adequately add 1 to each element stored in values?
- What is the value of values.length?
- What is returned by values[3]?
- 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?
- 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?
- 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.
- An object may be made up of other objects.
- Method decomposition is the process of creating overloaded versions of a method that do the same thing, but operate on different data types.
- The println method on System.out is overloaded.
- A method defined without a return statement will cause a compile error.
- If a method takes a double as a parameter, you could pass it an int as the actual parameter.
- The different versions of an overloaded method are differentiated by their signatures.
- The number and types of the actual parameters must match the number and types of the formal parameters.
- The return statement must be followed a single variable that contains the value to be returned.