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Home Java Programming Garbage Collections See What Others Are Saying!
  • Question
  • When is the Float object, created in line 3, eligible for garbage collection?
    public Object m() 
    {  
        Object o = new Float(3.14F); 
        Object [] oa = new Object[l];
        oa[0] = o; /* Line 5 */
        o = null;  /* Line 6 */
        oa[0] = null; /* Line 7 */
        return o; /* Line 8 */
    }
    


  • Options
  • A. just after line 5
  • B. just after line 6
  • C. just after line 7
  • D. just after line 8

  • Correct Answer
  • just after line 7 

    Explanation
    Option A is wrong. This simply copies the object reference into the array.

    Option B is wrong. The reference o is set to null, but, oa[0] still maintains the reference to the Float object.

    Option C is correct. The thread of execution will then not have access to the object.


  • More questions

    • 1. What will be the output of the program?
      public class A
      { 
          void A() /* Line 3 */
          {
              System.out.println("Class A"); 
          } 
          public static void main(String[] args) 
          { 
              new A(); 
          } 
      }
      

    • Options
    • A. Class A
    • B. Compilation fails.
    • C. An exception is thrown at line 3.
    • D. The code executes with no output.
    • Discuss
    • 2. What will be the output of the program?
      class Test 
      {
          public static void main(String [] args) 
          {
              Test p = new Test();
              p.start();
          }
      
          void start() 
          {
              boolean b1 = false;
              boolean b2 = fix(b1);
              System.out.println(b1 + " " + b2);
          }
      
          boolean fix(boolean b1) 
          {
              b1 = true;
              return b1;
          }
      }
      

    • Options
    • A. true true
    • B. false true
    • C. true false
    • D. false false
    • Discuss
    • 3. What will be the output of the program?
      class Test 
      {
          static int s;
          public static void main(String [] args) 
          {
              Test p = new Test();
              p.start();
              System.out.println(s);
          }
      
          void start() 
          {
              int x = 7;
              twice(x);
              System.out.print(x + " ");
          }
      
          void twice(int x) 
          {
              x = x*2;
              s = x;
          }
      }
      

    • Options
    • A. 7 7
    • B. 7 14
    • C. 14 0
    • D. 14 14
    • Discuss
    • 4. You want a class to have access to members of another class in the same package. Which is the most restrictive access that accomplishes this objective?

    • Options
    • A. public
    • B. private
    • C. protected
    • D. default access
    • Discuss
    • 5. What will be the output of the program?
      class Super
      { 
          public int i = 0; 
      
          public Super(String text) /* Line 4 */
          {
              i = 1; 
          } 
      } 
      
      class Sub extends Super
      {
          public Sub(String text)
          {
              i = 2; 
          } 
      
          public static void main(String args[])
          {
              Sub sub = new Sub("Hello"); 
              System.out.println(sub.i); 
          } 
      }
      

    • Options
    • A. 0
    • B. 1
    • C. 2
    • D. Compilation fails.
    • Discuss
    • 6. What will be the output of the program (in jdk1.6 or above)?
      public class BoolTest 
      {
          public static void main(String [] args) 
          {
              Boolean b1 = new Boolean("false");
              boolean b2;
              b2 = b1.booleanValue();
              if (!b2) 
              {
                  b2 = true;
                  System.out.print("x ");
              }
              if (b1 & b2) /* Line 13 */
              {
                  System.out.print("y ");
              }
              System.out.println("z");
          }
      }
      

    • Options
    • A. z
    • B. x z