Java反射的两种使用方法

1.创建User.java

package com.tao.test;

public class User {

    private String name;
    private int id;
    public User() {
        
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    

}

2.main方法

package com.tao.test;

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

public class test {

    public static void main(String[] args) throws Exception, SecurityException {
        //第一种 Constructor<?>方法
        Constructor<?> a = User.class.getDeclaredConstructor();
        a.setAccessible(true);
        User b = (User)a.newInstance();
        b.setId(1);//id字段
        b.setName("test");//name字段
        System.out.println(b.getId()+" "+b.getName());
        
        //第二种 Class<?>方法
        Class<?> c = Class.forName("com.tao.test.User");
        Field idF = c.getDeclaredField("id");//id字段
        idF.setAccessible(true);
        Object o = c.newInstance();
        idF.set(o, 2);
        
        Field nameF = c.getDeclaredField("name");//name字段
        nameF.setAccessible(true);
        Object name = c.newInstance();
        nameF.set(name, "jack");
        System.out.println(idF.get(o)+" "+nameF.get(name));
        
        //普通new
        User user = new User();
        user.setId(3);
        user.setName("tery");
        System.out.println(user.getId()+" "+user.getName()+" "+user.getClass());
    }

}

3.控制台输出：

1 test
2 jack
3 tery class com.tao.test.User