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Home Java Programming Objects and Collections See What Others Are Saying!
  • Question
  • What will be the output of the program?
    public static void main(String[] args) 
    {
        Object obj = new Object() 
        {
            public int hashCode() 
            {
                return 42;
            }
        }; 
        System.out.println(obj.hashCode()); 
    }
    


  • Options
  • A. 42
  • B. Runtime Exception
  • C. Compile Error at line 2
  • D. Compile Error at line 5

  • Correct Answer
  • 42 

    Explanation
    This code is an example of an anonymous inner class. They can be declared to extend another class or implement a single interface. Since they have no name you can not use the "new" keyword on them.

    In this case the annoynous class is extending the Object class. Within the {} you place the methods you want for that class. After this class has been declared its methods can be used by that object in the usual way e.g. objectname.annoymousClassMethod()


    More questions

    • 1. What will be the output of the program?
      public class Test 
      {
          public static void main(String [] args) 
          {
              signed int x = 10;
              for (int y=0; y<5; y++, x--)
                  System.out.print(x + ", ");
          }
      }
      

    • Options
    • A. 10, 9, 8, 7, 6,
    • B. 9, 8, 7, 6, 5,
    • C. Compilation fails.
    • D. An exception is thrown at runtime.
    • Discuss
    • 2. Which two of the following statements, inserted independently, could legally be inserted into missing section of this code?
      1. boolean test = (Component instanceof t);
      2. boolean test = (t instanceof Ticker);
      3. boolean test = t.instanceof(Ticker);
      4. boolean test = (t instanceof Component);
          
      import java.awt.*;
      class Ticker extends Component 
      {
          public static void main (String [] args) 
          {
              Ticker t = new Ticker();
              /* Missing Statements? */
          }
      }
      

    • Options
    • A. 1 and 4
    • B. 2 and 3
    • C. 1 and 3
    • D. 2 and 4
    • Discuss
    • 3. What will be the output of the program?
      class Test 
      {
          public static void main(String [] args) 
          {
              int x=20;
              String sup = (x < 15)? "small" : (x < 22)? "tiny" : "huge";
              System.out.println(sup);
          }
      }
      

    • Options
    • A. small
    • B. tiny
    • C. huge
    • D. Compilation fails
    • Discuss
    • 4. Which statement, inserted at line 10, creates an instance of Bar?
      class Foo 
      {
          class Bar{ }
      }
      class Test 
      {
          public static void main (String [] args) 
          {
              Foo f = new Foo();
              /* Line 10: Missing statement? */
          }
      }
      

    • Options
    • A. Foo.Bar b = new Foo.Bar();
    • B. Foo.Bar b = f.new Bar();
    • C. Bar b = new f.Bar();
    • D. Bar b = f.new Bar();
    • Discuss
    • 5. What line of code should replace the missing statement to make this program compile?
      /* Missing Statement? */
      public class foo 
      {
          public static void main(String[]args)throws Exception 
          {
              java.io.PrintWriter out = new java.io.PrintWriter(); 
              new java.io.OutputStreamWriter(System.out,true); 
              out.println("Hello"); 
          } 
      }
      

    • Options
    • A. No statement required.
    • B. import java.io.*;
    • C. include java.io.*;
    • D. import java.io.PrintWriter;
    • Discuss
    • 6. When is the B object, created in line 3, eligible for garbage collection?
      void start() {  
          A a = new A(); 
          B b = new B(); 
          a.s(b);  
          b = null; /* Line 5 */
          a = null;  /* Line 6 */
          System.out.println("start completed"); /* Line 7 */
      } 
      

    • Options
    • A. after line 5
    • B. after line 6
    • C. after line 7
    • D. There is no way to be absolutely certain.
    • Discuss
    • 7. Which is a reserved word in the Java programming language?

    • Options
    • A. method
    • B. native
    • C. subclasses
    • D. reference
    • E. array
    • Discuss
    • 8. Which statement is true for the class java.util.ArrayList?

    • Options
    • A. The elements in the collection are ordered.
    • B. The collection is guaranteed to be immutable.
    • C. The elements in the collection are guaranteed to be unique.
    • D. The elements in the collection are accessed using a unique key.
    • Discuss
    • 9. What will be the output of the program?
      public class Test 
      { 
          public static void main(String[] args) 
          {
              final StringBuffer a = new StringBuffer(); 
              final StringBuffer b = new StringBuffer(); 
      
              new Thread() 
              { 
                  public void run() 
                  {
                      System.out.print(a.append("A")); 
                      synchronized(b) 
                      { 
                          System.out.print(b.append("B")); 
                      } 
                  } 
              }.start(); 
                  
              new Thread() 
              {
                  public void run() 
                  {
                      System.out.print(b.append("C")); 
                      synchronized(a) 
                      {
                          System.out.print(a.append("D")); 
                      } 
                  } 
              }.start(); 
          } 
      }
      

    • Options
    • A. ACCBAD
    • B. ABBCAD
    • C. CDDACB
    • D. Indeterminate output
    • Discuss
    • 10. Which is true about a method-local inner class?

    • Options
    • A. It must be marked final.
    • B. It can be marked abstract.
    • C. It can be marked public.
    • D. It can be marked static.
    • Discuss


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