Interface java Example Interview

 //interface Only public, static and final are allowed.

//No. Interfaces can’t have constructors.
interface Test{

    static  int s=2;
    final int d=4;
    void get();
    int getmultiple();

}


// initializers not allowed in interfaces
/*interface demoStatic(){
    {  System.out.println("empty implemented");}
    
    static{
         System.out.println("static implemented"); 
    }
}*/


interface B{
    int getdivide(int i);
    //  int getadd();//implementation is required in Class A
}

class A implements B{

    public int getdivide(int i ){
        return  i*i;
    }
}


class p{

    interface Q{
        int i=111;
    }
}

interface NextTest extends Test{
    int t=5;
    void get();

    int getadd();

    //  int getValue();//Demo is not abstract and does not override abstract method getValue() in NextTest
}

class Demo implements Test, NextTest {

    public int getadd(){
        return d+t;
    }

    public int getmultiple(){
        return d*t;
    }
    public void get(){
        System.out.println("demo get method implemented");
    }


}
class XDemo extends Demo{

}

/*class XXDemo implements NextTest{
    void methodD(){
        i=4;
        //No, because interface fields are static and 
        //final by default and you can’t change
        //their value once they are initialized. In the above code, methodB() 
        //is changing value of interface field A.i. It shows compile time error.
    }
}*/


public class MyClass {
    public static void main(String args[]) {

        System.out.println("Interface");

        Test s=new XDemo();
        s.get();
        //  System.out.println("sum : "+ s.getadd());//it will check in Test interface error not found

        System.out.println("multiple : "+ s.getmultiple());
        NextTest st=new XDemo();
        System.out.println("add : "+ st.getadd());

        // XDemo s=new NextTest();//NextTest is abstract; cannot be instantiated
        XDemo sp=new XDemo();
        System.out.println("addd : "+ sp.getadd());
        System.out.println("multiple : "+ sp.getmultiple());



        B newS=new A();

        System.out.println("divide : "+ newS.getdivide(12));
        // p ps=new Q();
        B bs=new B(){
            public int getdivide(int i){
                return i*i;          }

        };

        System.out.println("divide : "+  bs.getdivide(12));
    }
}