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Sun Certified Java Programmer

Practice Exam

What will happen if you compile/run this code?

1:     public class Q1 extends Thread
2:     {
3:         public void run()
4:         {
5:            System.out.println("Before start method");
6:            this.stop();        
7:            System.out.println("After stop method");
8:        }
9:        
10:        public static void main(String[] args)
11:        {
12:            Q1 a = new Q1();
13:            a.start();
14:        }
15:    }

A) Compilation error at line 7.
B) Runtime exception at line 7.
C) Prints "Before start method" and "After stop method".
D) Prints "Before start method" only.

Answer

Question 2

What will happen if you compile/run the following code?

1:    class Test
2:    {
3:  static void show()
4:  {
5:      System.out.println("Show method in Test class");
6:  }
7:}
8:
9:    public class Q2 extends Test
10:   {
11: static void show()
12: {
13:     System.out.println("Show method in Q2 class");
14: }
15: public static void main(String[] args)
16: {
17:     Test t = new Test();
18:     t.show();
19:     Q2 q = new Q2();
20:     q.show();
21:     
22:     t = q; 
23:     t.show();
24:
25:     q = t; 
26:     q.show();
27: }
28: }

A) prints "Show method in Test class"
          "Show method in Q2 class"
          "Show method in Q2 class"
          "Show method in Q2 class"
          
B) prints "Show method in Test class"
          "Show method in Q2 class"
          "Show method in Test class"
          "Show method in Test class"

C) prints "Show method in Test class"
          "Show method in Q2 class"
          "Show method in Test class"
          "Show method in Q2 class"
          
D) Compilation error.

            

Answer 

The following code will give

1:    class Test
2:    {
3:      void show()
4:      {
5:      System.out.println("non-static method in Test");
6:  }
7:    }
8:    public class Q3 extends Test
9:    {
10:     static void show()
11: {
12:     System.out.println("Overridden non-static method in Q3");
13: }
14:            
15:       public static void main(String[] args)
16:       {
17:              Q3 a = new Q3();
18:        }
19:    }

A) Compilation error at line 3.
B) Compilation error at line 10.
C) No compilation error, but runtime exception at line 3.
D) No compilation error, but runtime exception at line 10.

Answer

The following code will give


1:    class Test
2:    {
3:      static void show()
4:      {
5:          System.out.println("Static method in Test");
6:      }
7:    }
8:    public class Q4 extends Test
9:    {
10:     void show()
11: {
12:     System.out.println("Overridden static method in Q4");
13: }
14: public static void main(String[] args)
15: {
16: }
17:    }

A) Compilation error at line 3.
B) Compilation error at line 10.
C) No compilation error, but runtime exception at line 3.
D) No compilation error, but runtime exception at line 10.

Answer

The following code will print

1:    int i = 1;
2:    i <<= 31;
3:    i >>= 31;
4:    i >>= 1;
5:
6:    int j = 1;
7:    j <<= 31;
8:    j >>= 31;
9:      
10:    System.out.println("i = " +i );
11:    System.out.println("j = " +j);

A) i = 1
   j = 1

B) i = -1
   j = 1
   
C) i = 1
   j = -1
   
D) i = -1
   j = -1
   
Answer  

The following code will print

1:    Double a = new Double(Double.NaN);
2:    Double b = new Double(Double.NaN);
3:              
4:    if( Double.NaN == Double.NaN )
5:  System.out.println("True");
6:    else
7:  System.out.println("False");
8:          
9:    if( a.equals(b) )
10: System.out.println("True");
11:   else
12: System.out.println("False");

A) True
   True
   
B) True
   False
   
C) False
   True
   
D) False
   False
   
Answer

1:    if( new Boolean("true") == new Boolean("true")) 
2:        System.out.println("True");
3:    else
4:        System.out.println("False"); 

A) Compilation error.
B) No compilation error, but runtime exception.
C) Prints "True".
D) Prints "False".

Answer

 

1:    public class Q8
2:    {
3:        int i = 20;
4:        static 
5:        {
6:            int i = 10;
7:            
8:        }
9:        public static void main(String[] args)
10:        {
11:             Q8 a = new Q8();
12:             System.out.println(a.i);
13:        }
14:    }        

A) Compilation error, variable "i" declared twice.
B) Compilation error, static initializers for initialization purpose only.
C) Prints 10.
D) Prints 20.

Answer

 
The following code will give 

1:     Byte b1 = new Byte("127");
2:
3:     if(b1.toString() == b1.toString())
4:        System.out.println("True");
5:    else
6:        System.out.println("False");

A) Compilation error, toString() is not avialable for Byte.
B) Prints "True".
C) Prints "False".

Answer

What will happen if you compile/run this code?

1:    public class Q10
2:    {
3:      public static void main(String[] args)
4:      {
5:          int i = 10;
6:          int j = 10;
7:          boolean b = false;
8:          
9:          if( b = i == j)
10:            System.out.println("True");
11:         else
12:        System.out.println("False");
13: }
14:    }

A) Compilation error at line 9 .
B) Runtime error exception at line 9.
C) Prints "True".
D) Prints "Fasle".

Answer

    D.  After the execution of stop() method, thread won't execute any more statements.

Back to Question 1

    D. Explicit casting is required at line 25.

Back to Question 2

    B. You cann't override an non-static method with static method.

Back to Question 3

    B. You cann't override a static method with non-static method.

Back to Question 4

    D.

Back to Question 5

    C.

Back to Question 6

    D.

Back to Question 7

    D.  Here the variable '"i" defined in static initializer is local to that block only. 
        The statements in the static initializers will be executed (only once) when the class is first created.

Back to Question 8

    C.

Back to Question 9

    C. Conditional operators have high precedence than assignment operators.

Back to Question 10