abstract class Subject {
  abstract public void request();
}

public class RealSubject extends Subject {
  public void request() {
    System.out.println("RealSubject request()メソッド");
  }
}

public class Proxy extends Subject{
  RealSubject realSubject;

  public void request() {
    if (realSubject==null) {
      realSubject = new RealSubject();
    }
    realSubject.request();
  }
}

public class Client {
  public static void main(String[] args) {
    Proxy p = new Proxy();
    p.request();
  }
}

C:\JavaHello\Proxy>java Client
RealSubject request()メソッド

C:\JavaHello\Proxy>