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Java Programming :: Objects and Collections

  1. What will be the output of the program?

      public class Test
      {     
         public static void main (String[] args)  
         {        
            String foo = args[1];       
            String bar = args[2];        
            String baz = args[3];      
            System.out.println("baz = " + baz); /* Line 8 */     
       }  
    } 

     

    And the command line invocation:

    > java Test red green blue

     

     

  2. A.

    baz =

    B.

    baz = null

    C.

    baz = blue

    D.

    Runtime Exception


  3. What will be the output of the program?

    public class Test 
    {    
        public static void main (String args[])    
        {        
             String str = NULL;      
             System.out.println(str);    
       }  
    } 

     

  4. A.

    NULL

    B.

    Compile Error

    C.

    Code runs but no output

    D.

    Runtime Exception


  5. 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 */     
         }
       
       } 
    

  6. 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.


  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]);   
       }  
    } 
    

  8. A.

    B.

    null

    C.

    Compile Error

    D.

    NullPointerException at runtime


  9. What will be the output of the program?

      import java.util.*;
      class I
      {    
           public static void main (String[] args)  
           {         
               Object i = new ArrayList().iterator();     
               System.out.print((i instanceof List)+",");          
               System.out.print((i instanceof Iterator)+",");          
               System.out.print(i instanceof ListIterator);  
        }  
    }
    

  10. A.

    Prints: false, false, false

    B.

    Prints: false, false, true

    C.

    Prints: false, true, false

    D.

    Prints: false, true, true


  11. 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]);      
       }
     } 
    

  12. A.

    f[0] = 0

    B.

    f[0] = 0.0

    C.

    Compile Error

    D.

    Runtime Exception


  13. 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);   
       }  
    }
    

  14. A.

    Prints: false,false,false

    B.

    Prints: false,false,true

    C.

    Prints: false,true,false

    D.

    Prints: true,false,false


  15. 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");  
     Ierator it = map.iterator();
     while (it.hasNext() )
      {    
         System.out.print( it.next() + " " ); 
      } 
    

  16. A.

    one two three four

    B.

    four three two one

    C.

    four one three two

    D.

    one two three four one


  17. 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()); 
     } 
    

  18. A.

    42

    B.

    Runtime Exception

    C.

    Compile Error at line 2

    D.

    Compile Error at line 5