反射机制1

Person类

package day1;

public class Person {
    private String name;
    public int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    private Person(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }
    @Override
    public String toString() {
        return "姓名："+ name + "，年龄：" + age;
    }
    public String show(){
        return this.name+" , "+this.age;
    }
    private String showNation(String nation){
        return "我来自"+nation;
    }
}

利用反射机制操作Person对象

package day1;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class ReflectionDemo1 {
    //反射机制，允许程序在运行期间获取类的内部信息，操作对象的内部属性和方法
    //加载类后，产生Class类对象，含有类的完整信息
    public static void main(String[] args) throws Exception {
        Person p1=new Person("张三",20);
        p1.age=30;
        System.out.println(p1.show());

        //通过反射，创建对象
        Class c1=Person.class;
        Constructor cons=c1.getConstructor(String.class,int.class);
        Person p2=(Person) cons.newInstance("李四",40);
        System.out.println(p2);
        //调用对象的指定属性
        Field age=c1.getDeclaredField("age");
        age.set(p2,50);
        System.out.println(p2);
        //调用指定方法
        Method show=c1.getDeclaredMethod("show");
        System.out.println(show.invoke(p1));

        //通过反射，可以调用Person类的私有结构，如私有构造器、属性、方法
        System.out.println("******************************");
        Constructor cons1=c1.getDeclaredConstructor(String.class);
        cons1.setAccessible(true);
        Person p3=(Person) cons1.newInstance("WangWu");
        System.out.println(p3);

        Field name=c1.getDeclaredField("name");
        name.setAccessible(true);
        name.set(p3,"ZhaoLiu");
        System.out.println(p3);

        Method showNation=c1.getDeclaredMethod("showNation", String.class);
        showNation.setAccessible(true);
        System.out.println(showNation.invoke(p3,"中国"));
    }
}