Java interface programming questions

• We can develop interfaces by using "interface" keyword. 
• A class will implements all the methods in an interface.
• By default interface methods are abstract.
• Lets see some interesting java programming interview questions on interfaces.
• Interface programming questions in java

Java interface interview programs part 1: interface programming java

Program #1: what will happen if we define normal methods in interface

1. package interfaceinverviewprograms.instanceofjava;
2. public interface A{
3.  
4. /**
5. * @java interface  interview programming  questions and answers for freshers and experienced
6.  */
7.   
8. void show() {
9.         
10.         System.out.println("Hello world");
11.  
12.     }
13. }

Program #2:java interview programs to practice: Non static variables in interface

1. package interfaceinverviewprograms.instanceofjava;
2. public interface A{
3.  
4. /**
5. * @java interface  interview programming  questions and answers for freshers and experienced
6.  */
7.   
8. int a,b;
9. 
   
10. }

Program #3:java interview programs to practice: which modifiers interface allows

1. package interfaceinverviewprograms.instanceofjava;
2. public interface A{
3.  
4. /**
5. * @java interface  interview programming  questions and answers for freshers and experienced
6.  */
7.   
8. private int x;
9. protected int y;
10. 
    
11. }

1. compile time error: Illegal modifier for the interface field A.x; only
2. public, static & final are permitted
3. compile time error: Illegal modifier for the interface field A.y; only
4. public, static & final are permitted

Program #4:java interview programs to practice: interface allows constructor?

1. package interfaceinverviewprograms.instanceofjava;
2. public interface A{
3.  
4. /**
5. * @java interface  interview programming  questions and answers for freshers and experienced
6.  */
7. A(){
8.  
9. }
10. 
    
11. }

1. Compile time error: interface cannot allow constructor