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Home Java Programming Inner Classes See What Others Are Saying!
  • Question
  • 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();

  • Correct Answer
  • Foo.Bar b = f.new Bar(); 

    Explanation
    Option B is correct because the syntax is correct-using both names (the enclosing class and the inner class) in the reference declaration, then using a reference to the enclosing class to invoke new on the inner class.

    Option A, C and D all use incorrect syntax. A is incorrect because it doesn't use a reference to the enclosing class, and also because it includes both names in the new.

    C is incorrect because it doesn't use the enclosing class name in the reference variable declaration, and because the new syntax is wrong.

    D is incorrect because it doesn't use the enclosing class name in the reference variable declaration.


  • More questions

    • 1. Which two statements are equivalent?

      1. 16*4
      2. 16>>2
      3. 16/2^2
      4. 16>>>2

    • Options
    • A. 1 and 2
    • B. 2 and 4
    • C. 3 and 4
    • D. 1 and 3
    • Discuss
    • 2. What two statements are true about properly overridden hashCode() and equals() methods?

      1. hashCode() doesn't have to be overridden if equals() is.
      2. equals() doesn't have to be overridden if hashCode() is.
      3. hashCode() can always return the same value, regardless of the object that invoked it.
      4. equals() can be true even if it's comparing different objects.

    • Options
    • A. 1 and 2
    • B. 2 and 3
    • C. 3 and 4
    • D. 1 and 3
    • Discuss
    • 3. Which is a valid keyword in java?

    • Options
    • A. interface
    • B. string
    • C. Float
    • D. unsigned
    • Discuss
    • 4. What will be the output of the program?
      int i = 1, j = 10; 
      do 
      {
          if(i++ > --j) /* Line 4 */
          {
              continue; 
          } 
      } while (i < 5); 
      System.out.println("i = " + i + "and j = " + j); /* Line 9 */
      

    • Options
    • A. i = 6 and j = 5
    • B. i = 5 and j = 5
    • C. i = 6 and j = 6
    • D. i = 5 and j = 6
    • Discuss
    • 5. What will be the output of the program?
      int i = 0; 
      while(1) 
      {
          if(i == 4) 
          {
              break;
          } 
          ++i; 
      } 
      System.out.println("i = " + i);
      

    • Options
    • A. i = 0
    • B. i = 3
    • C. i = 4
    • D. Compilation fails.
    • Discuss
    • 6. What will be the output of the program?
      public class Test 
      {
          public int aMethod()
          {
              static int i = 0;
              i++;
              return i;
          }
          public static void main(String args[])
          {
              Test test = new Test();
              test.aMethod();
              int j = test.aMethod();
              System.out.println(j);
          }
      }
      

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. Compilation fails.
    • Discuss
    • 7. What will be the output of the program?
      int x = l, y = 6; 
      while (y--) 
      {
          x++; 
      } 
      System.out.println("x = " + x +" y = " + y);
      

    • Options
    • A. x = 6 y = 0
    • B. x = 7 y = 0
    • C. x = 6 y = -1
    • D. Compilation fails.
    • Discuss
    • 8. What will be the output of the program?
      class MyThread extends Thread 
      { 
          MyThread() {} 
          MyThread(Runnable r) {super(r); } 
          public void run() 
          { 
              System.out.print("Inside Thread ");
          } 
      } 
      class MyRunnable implements Runnable 
      { 
          public void run() 
          { 
              System.out.print(" Inside Runnable"); 
          } 
      } 
      class Test 
      {  
          public static void main(String[] args) 
          { 
              new MyThread().start(); 
              new MyThread(new MyRunnable()).start(); 
          } 
      }
      

    • Options
    • A. Prints "Inside Thread Inside Thread"
    • B. Prints "Inside Thread Inside Runnable"
    • C. Does not compile
    • D. Throws exception at runtime
    • Discuss
    • 9. Which statement is true?

    • Options
    • A. Assertions can be enabled or disabled on a class-by-class basis.
    • B. Conditional compilation is used to allow tested classes to run at full speed.
    • C. Assertions are appropriate for checking the validity of arguments in a method.
    • D. The programmer can choose to execute a return statement or to throw an exception if an assertion fails.
    • Discuss
    • 10. What will be the output of the program?
      class Two 
      {
          byte x;
      }
      
      class PassO 
      {
          public static void main(String [] args) 
          {
              PassO p = new PassO();
              p.start();
          }
      
          void start() 
          {
              Two t = new Two();
              System.out.print(t.x + " ");
              Two t2 = fix(t);
              System.out.println(t.x + " " + t2.x);
          }
      
          Two fix(Two tt) 
          {
              tt.x = 42;
              return tt;
          }
      }
      

    • Options
    • A. null null 42
    • B. 0 0 42
    • C. 0 42 42
    • D. 0 0 0
    • Discuss


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