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  • Question
  • What will be the output of the program?
    public class Switch2 
    {
        final static short x = 2;
        public static int y = 0;
        public static void main(String [] args) 
        {
            for (int z=0; z < 3; z++) 
            {
                switch (z) 
                {
                    case y: System.out.print("0 ");   /* Line 11 */
                    case x-1: System.out.print("1 "); /* Line 12 */
                    case x: System.out.print("2 ");   /* Line 13 */
                }
            }
        }
    }
    


  • Options
  • A. 0 1 2
  • B. 0 1 2 1 2 2
  • C. Compilation fails at line 11.
  • D. Compilation fails at line 12.

  • Correct Answer
  • Compilation fails at line 11. 

    Explanation
    Case expressions must be constant expressions. Since x is marked final, lines 12 and 13 are legal; however y is not a final so the compiler will fail at line 11.

    Flow Control problems


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    • 1. What will be the output of the program?
      public class If1 
      {
          static boolean b;
          public static void main(String [] args) 
          {
              short hand = 42;
              if ( hand < 50 && !b ) /* Line 7 */
                  hand++;
              if ( hand > 50 );     /* Line 9 */
              else if ( hand > 40 ) 
              {
                  hand += 7;
                  hand++;    
              }
              else
                  --hand;
              System.out.println(hand);
          }
      }
      

    • Options
    • A. 41
    • B. 42
    • C. 50
    • D. 51
    • Discuss
    • 2. What will be the output of the program?
      for (int i = 0; i < 4; i += 2) 
      { 
          System.out.print(i + " "); 
      } 
      System.out.println(i); /* Line 5 */
      

    • Options
    • A. 0 2 4
    • B. 0 2 4 5
    • C. 0 1 2 3 4
    • D. Compilation fails.
    • Discuss
    • 3. What will be the output of the program?
      public class Delta 
      { 
          static boolean foo(char c) 
          {
              System.out.print(c); 
              return true; 
          } 
          public static void main( String[] argv ) 
          {
              int i = 0; 
              for (foo('A'); foo('B') && (i < 2); foo('C')) 
              {
                  i++; 
                  foo('D'); 
              } 
          } 
      }
      

    • Options
    • A. ABDCBDCB
    • B. ABCDABCD
    • C. Compilation fails.
    • D. An exception is thrown at runtime.
    • Discuss
    • 4. What will be the output of the program?
      public class SwitchTest 
      {  
          public static void main(String[] args) 
          {
              System.out.println("value =" + switchIt(4)); 
          } 
          public static int switchIt(int x) 
          {
              int j = 1;  
              switch (x) 
              { 
                  case l: j++; 
                  case 2: j++;  
                  case 3: j++; 
                  case 4: j++; 
                  case 5: j++; 
                  default: j++; 
                  } 
              return j + x;  
          } 
      }
      

    • Options
    • A. value = 2
    • B. value = 4
    • C. value = 6
    • D. value = 8
    • Discuss
    • 5. What will be the output of the program?
      int x = 3; 
      int y = 1; 
      if (x = y) /* Line 3 */
      {
          System.out.println("x =" + x); 
      }
      

    • Options
    • A. x = 1
    • B. x = 3
    • C. Compilation fails.
    • D. The code runs with no output.
    • Discuss
    • 6. What will be the output of the program?
      TreeSet map = new TreeSet();
      map.add("one");
      map.add("two");
      map.add("three");
      map.add("four");
      map.add("one");
      Iterator it = map.iterator();
      while (it.hasNext() ) 
      {
          System.out.print( it.next() + " " );
      }
      

    • Options
    • A. one two three four
    • B. four three two one
    • C. four one three two
    • D. one two three four one
    • Discuss
    • 7. What will be the output of the program?
      public class Test 
      { 
          private static int[] x; 
          public static void main(String[] args) 
          { 
              System.out.println(x[0]); 
          } 
      }
      

    • Options
    • A. 0 
    • B. null
    • C. Compile Error
    • D. NullPointerException at runtime
    • Discuss
    • 8. What will be the output of the program?
      import java.util.*; 
      class H 
      {
          public static void main (String[] args) 
          { 
              Object x = new Vector().elements(); 
              System.out.print((x instanceof Enumeration)+","); 
              System.out.print((x instanceof Iterator)+","); 
              System.out.print(x instanceof ListIterator); 
          } 
      }
      

    • Options
    • A. Prints: false,false,false
    • B. Prints: false,false,true
    • C. Prints: false,true,false
    • D. Prints: true,false,false
    • Discuss
    • 9. What will be the output of the program?
      package foo; 
      import java.util.Vector; /* Line 2 */
      private class MyVector extends Vector 
      {
          int i = 1; /* Line 5 */
          public MyVector() 
          { 
              i = 2; 
          } 
      } 
      public class MyNewVector extends MyVector 
      {
          public MyNewVector () 
          { 
              i = 4; /* Line 15 */
          } 
          public static void main (String args []) 
          { 
              MyVector v = new MyNewVector(); /* Line 19 */
          } 
      }
      

    • Options
    • A. Compilation will succeed.
    • B. Compilation will fail at line 3.
    • C. Compilation will fail at line 5.
    • D. Compilation will fail at line 15.
    • Discuss
    • 10. What will be the output of the program?
      public class Test 
      { 
          private static float[] f = new float[2]; 
          public static void main (String[] args) 
          {
              System.out.println("f[0] = " + f[0]); 
          } 
      }
      

    • Options
    • A. f[0] = 0
    • B. f[0] = 0.0
    • C. Compile Error
    • D. Runtime Exception
    • Discuss


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