java多态（接口与实现）之静态代理

//废话不多说，直接上代码
public class Test {
static interface Subject{
void sayHi();
void sayHello();
}

static class SubjectImpl implements Subject{

@Override
public void sayHi() {
System.out.println("hi");
}

@Override
public void sayHello() {
System.out.println("hello");
}
}

static class SubjectImplProxy implements Subject{
private Subject target;

public SubjectImplProxy(Subject target) {
this.target=target;
}

@Override
public void sayHi() {
System.out.print("say:");
target.sayHi();
}

@Override
public void sayHello() {
System.out.print("say:");
target.sayHello();
}
}

public static void main(String[] args) {
Subject subject=new SubjectImpl();
Subject subjectProxy=new SubjectImplProxy(subject);
subjectProxy.sayHi();
subjectProxy.sayHello();
}
}
//直接说main方法的调用过程：
subjectProxy.sayHi()调用SubjectImplProxy这个实现类的sayHi（）方法，这个时候SubjectImplProxy类中的变量target已经被实例化，实例化的实现类为SubjectImpl ，所以target.sayHi()这个方法调用SubjectImpl 这个实现类的sayHi()方法。
打印结果：say:hi
say:hello