Yes, we can have private methods or private static methods in an interface in Java 9. We can use these methods to remove the code redundancy. Private methods can be useful or accessible only within that interface only. We can't access or inherit private methods from one interface to another interface or class.
Syntax
interface <interface-name> {
private static void methodName() {
// some statements
}
private void methodName() {
// some statements
}
}Example
interface Java9Interface {
public abstract void method1();
public default void method2() {
method4();
method5();
System.out.println("Inside default method");
}
public static void method3() {
method5(); // static method inside other static method
System.out.println("Inside static method");
}
private void method4() { // private method
System.out.println("Inside private method");
}
private static void method5() { // private static method
System.out.println("Inside private static method");
}
}
public class PrivateStaticMethodTest implements Java9Interface {
@Override
public void method1() {
System.out.println("Inside abstract method");
}
public static void main(String args[]) {
Java9Interface instance = new PrivateStaticMethodTest();
instance.method1();
instance.method2();
Java9Interface.method3();
}
}Output
Inside abstract method Inside private method Inside private static method Inside default method Inside private static method Inside static method