import java.lang.reflect.Field;

import java.lang.reflect.Method;

import java.util.ArrayList;

public class Person {

    private String name;//私有属性

    public String address;

    public Person(String name){

        this.name=name;

    } 

    private void setAddress(String address){ //私有方法

        this.address=address;

    } 

    public static void main(String[] args) {

        try{

            Person person=new Person("zhangsan");

            Class<Person> cls=Person.class;

            //获得私有方法

            Method method=cls.getDeclaredMethod("setAddress", new Class[]{String.class});

            //设置私有方法可以被访问

            method.setAccessible(true);

            //调用私有方法

            method.invoke(person, new Object[]{"BJUT"});

            System.out.println(person.address);//输出BJUT 

            //访问私有变量

            Field field=cls.getDeclaredField("name");

            field.setAccessible(true);

            field.set(person, "test中国");

            System.out.println(field.get(person));//输出zhangsan 

            ArrayList<String> test = new ArrayList<String>(1000);

            Class<ArrayList> tcls = ArrayList.class; 

            field = tcls.getDeclaredField("size");

            field.setAccessible(true);

            field.set(test, 100);

            System.out.println(field.get(test));

            System.out.println(test.size());

        }catch(Exception ex){

            ex.printStackTrace();

        } 

    }

    public class Test {

        private String name;//私有属性

    }

}