Private method in interface - Java 9

InternalPrivateMethodMain.java

package com.java9r;

import java.util.*;

/**
 * @author Ravi
 *
 */
public class InternalPrivateMethodMain implements InternalPrivateMethod {

 public static void main(String[] args) {
  List<String> list = new ArrayList<>();
  list.add("Product 1");
  list.add("Product 2");
  list.add("Product 3");
  list.add("Product 4");
  list.add("Product 5");

  InternalPrivateMethod internalprivatemethod = new InternalPrivateMethodMain();

  List<String> list2 = new ArrayList<>();

  list2 = internalprivatemethod.add(list);
  System.out.println("Private method in interface - Java 9");
  for (String s : list2) {
   System.out.println(s);
  }

 }

}

InternalPrivateMethod.java

package com.java9r;

import java.util.List;

/**
 * @author Ravi
 *
 */
public interface InternalPrivateMethod {
 default List<String> add(List<String> list) {

  return calling(list);
 }
  // from java8 static methed also use in interface
 private List<String> calling(List<String> list) {

  return list;
 }
}

Output

Private method in interface - Java 9
Product 1
Product 2
Product 3
Product 4
Product 5