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  • Question
  • What will be the output of the program?
    class MyThread extends Thread 
    {
        MyThread() 
        {
            System.out.print(" MyThread");
        }
        public void run() 
        {
            System.out.print(" bar");
        }
        public void run(String s) 
        {
            System.out.println(" baz");
        }
    }
    public class TestThreads 
    {
        public static void main (String [] args) 
        {
            Thread t = new MyThread() 
            {
                public void run() 
                {
                    System.out.println(" foo");
                }
            };
            t.start();
        }
    }
    


  • Options
  • A. foo
  • B. MyThread foo
  • C. MyThread bar
  • D. foo bar

  • Correct Answer
  • MyThread foo 

    Explanation
    Option B is correct because in the first line of main we're constructing an instance of an anonymous inner class extending from MyThread. So the MyThread constructor runs and prints "MyThread". The next statement in main invokes start() on the new thread instance, which causes the overridden run() method (the run() method defined in the anonymous inner class) to be invoked, which prints "foo"

    More questions

    • 1. 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
    • 2. 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
    • 3. 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
    • 4. Given that all methods of class FileOutputStream, including close(), throw an IOException, which of these is true?
      import java.io.*;
      public class MyProgram 
      {
          public static void main(String args[])
          {
              FileOutputStream out = null;
              try 
              {
                  out = new FileOutputStream("test.txt");
                  out.write(122);
              }
              catch(IOException io) 
              {
                  System.out.println("IO Error.");
              }
              finally 
              {
                  out.close();
              }
          }
      }
      

    • Options
    • A. This program will compile successfully.
    • B. This program fails to compile due to an error at line 4.
    • C. This program fails to compile due to an error at line 6.
    • D. This program fails to compile due to an error at line 18.
    • Discuss
    • 5. What will be the output of the program?
      public class Test 
      {
          public static void main(String [] args) 
          {
              int I = 1;
              do while ( I < 1 )
              System.out.print("I is " + I);
              while ( I > 1 ) ;
          }
      }
      

    • Options
    • A. I is 1
    • B. I is 1 I is 1
    • C. No output is produced.
    • D. Compilation error
    • Discuss
    • 6. What will be the output of the program?
      class MyThread extends Thread 
      {
          public static void main(String [] args) 
          {
              MyThread t = new MyThread();
              Thread x = new Thread(t);
              x.start(); /* Line 7 */
          }
          public void run() 
          {
              for(int i = 0; i < 3; ++i) 
              {
                  System.out.print(i + "..");
              }
          }
      }
      

    • Options
    • A. Compilation fails.
    • B. 1..2..3..
    • C. 0..1..2..3..
    • D. 0..1..2..
    • Discuss
    • 7. Which of the following is/are legal method declarations?

      1. protected abstract void m1();
      2. static final void m1(){}
      3. synchronized public final void m1() {}
      4. private native void m1();

    • Options
    • A. 1 and 3
    • B. 2 and 4
    • C. 1 only
    • D. All of them are legal declarations.
    • Discuss
    • 8. Which three statements are true?
      1. f1 == f2
      2. f1 == f3
      3. f2 == f1[1]
      4. x == f1[0]
      5. f == f1[0]
      import java.awt.Button;
      class CompareReference 
      {
          public static void main(String [] args) 
          {
              float f = 42.0f;
              float [] f1 = new float[2];
              float [] f2 = new float[2];
              float [] f3 = f1;
              long x = 42;
              f1[0] = 42.0f;
          }
      }
      

    • Options
    • A. 1, 2 and 3
    • B. 2, 4 and 5
    • C. 3, 4 and 5
    • D. 1, 4 and 5
    • Discuss
    • 9. Which one create an anonymous inner class from within class Bar?
      class Boo 
      {
          Boo(String s) { }
          Boo() { }
      }
      class Bar extends Boo 
      {
          Bar() { }
          Bar(String s) {super(s);}
          void zoo() 
          {
          // insert code here
          }
      }
      

    • Options
    • A. Boo f = new Boo(24) { };
    • B. Boo f = new Bar() { };
    • C. Bar f = new Boo(String s) { };
    • D. Boo f = new Boo.Bar(String s) { };
    • Discuss
    • 10. Which of the following code fragments inserted, will allow to compile?
      public class Outer 
      { 
          public void someOuterMethod() 
          {
              //Line 5 
          } 
          public class Inner { } 
          
          public static void main(String[] argv) 
          {
              Outer ot = new Outer(); 
              //Line 10
          } 
      } 
      

    • Options
    • A. new Inner(); //At line 5
    • B. new Inner(); //At line 10
    • C. new ot.Inner(); //At line 10
    • D. new Outer.Inner(); //At line 10
    • Discuss


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