What are the rules for private methods in interfaces in Java 9?

Java 9 addsprivatemethodsnew features ininterface. Private methods can be defined using theprivatemodifier. We can addprivateandprivatestaticmethodsin the interface of

Rules for private methods in interfaces:

• Having the body of a private method in the interface means that we cannot declare it as a normal abstract method as we usually do in interfaces. If we try to declare a private method without a body, then it may throw an error saying "This method requires a body and not a semicolon".
• We cannot useprivateandabstractmodifiers simultaneously in an interface.
• If we want to access a private method from a static method in the interface, then the method can be declared asPrivate static methodbecause we cannot make a static reference to anon-staticmethod .
• AA private static methodused in anon-staticcontext means that it can be called from thedefault methodin the interface.

Syntax

interface  { private methodName(parameters) { // some statements } }

Example

interface TestInterface { default void methodOne() { System.out.println("This is a Default method One..."); printValues(); // calling a private method } default void methodTwo() { System.out.println("This is a Default method Two..."); printValues(); // calling private method... } private void printValues() { // private method in an interface  System.out.println("methodOne() called"); System.out.println("methodTwo() called"); } } public class PrivateMethodInterfaceTest implements TestInterface { public static void main(String[] args) { TestInterface instance = new PrivateMethodInterfaceTest(); instance.methodOne(); instance.methodTwo(); } }

Output

This is a Default method One... methodOne() called methodTwo() called This is a Default method Two... methodOne() called methodTwo() called

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