Java 9 인터페이스의 개인 메소드에 대한 규칙은 무엇입니까?

<strong>interface <interface-name> {
   private methodName(parameters) {
      // some statements
   }
}</strong>

interface TestInterface {
   <strong>default </strong>void methodOne() {
      System.out.println("This is a Default method One...");
      printValues(); // calling a private method
   }
   <strong>default </strong>void methodTwo() {
      System.out.println("This is a Default method Two...");
      printValues(); // calling private method...
   }
   <strong>private </strong>void <strong>printValues</strong><strong>()</strong> { <strong>// private method in an interface
</strong>      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();
   }
}

<strong>This is a Default method One...
methodOne() called
methodTwo() called
This is a Default method Two...
methodOne() called
methodTwo() called</strong>