Interfaces

1

What is the output of this program?

interface calculate {
            int VAR = 0;
            void cal(int item);
        }
        class display implements calculate {
            int x;
          public  void cal(int item) {
                if (item<2)
                    x = VAR;
                else
                    x = item * item;            
            }
        }
 class interfaces {
 
            public static void main(String args[]) {
                display[] arr=new display[3];
 
               for(int i=0;i<3;i++)
               arr[i]=new display();
               arr[0].cal(0);    
               arr[1].cal(1);
               arr[2].cal(2);
               System.out.print(arr[0].x+" " + arr[1].x + " " + arr[2].x);
            }
        }
A. 0 1 2
B. 0 2 4
C. 0 0 4
D. 0 1 4

2

What is the output of this program?

    interface calculate {
        void cal(int item);
    }
    class displayA implements calculate {
        int x;
        public void cal(int item) {
            x = item * item;            
        }
    }
    class displayB implements calculate {
        int x;
        public void cal(int item) {
            x = item / item;            
        }
    }
    class interfaces {
        public static void main(String args[]) {
            displayA arr1 = new displayA;
            displayB arr2 = new displayB;
            arr1.x = 0;
            arr2.x = 0;      
            arr1.cal(2);
            arr2.cal(2);
            System.out.print(arr1.x + " " + arr2.x);
        }
    }
A. 0 0
B. 2 2
C. 4 1
D. 1 4

3

What is the output of this program?

 
    interface calculate {
        void cal(int item);
    }
    class display implements calculate {
        int x;
        public void cal(int item) {
            x = item * item;            
        }
    }
    class interfaces {
        public static void main(String args[]) {
            display arr = new display;
            arr.x = 0;      
            arr.cal(2);
            System.out.print(arr.x);
        }
    }  
A. 0
B. 2
C. 4
D. None of the mentioned

4

Which of the following package stores all the standard java classes?

A. lang
B. java
C. util
D. java.packages

5

Which of the following is incorrect statement about packages?

A. Interfaces specifies what class must do but not how it does.
B. Interfaces are specified public if they are to be accessed by any code in the program.
C. All variables in interface are implicitly final and static.
D. All variables are static and methods are public if interface is defined pubic.