class Student implements Person
{
public void show()
{
System.out.println("student run");
}
}
class ProxyStudent implements Person
{
private Student s;
public void show()
{
before();
if(s == null)//这个比较是什么意思，为什么不直接new一个Student对象呢？
{
s = new Student();
}
s.show();
after();
}
public void before()
{
System.out.println("do something before show");
}
public void after()
{
System.out.println("do something after show");
}
}
public class ProxyDemo {
public static void main(String[] args) {
// TODO Auto-generated method stub
ProxyStudent ps = new ProxyStudent();
ps.show();
}