反射机制调用构造方法

Vip类

package com.happy.bean;

public class Vip {
    int no;
    String name;
    String birth;
    boolean sex;

    public Vip() {
    }

    public Vip(int no) {
        this.no = no;
    }

    public Vip(int no, String name) {
        this.no = no;
        this.name = name;
    }

    public Vip(int no, String name, String birth) {
        this.no = no;
        this.name = name;
        this.birth = birth;
    }

    public Vip(int no, String name, String birth, boolean sex) {
        this.no = no;
        this.name = name;
        this.birth = birth;
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "Vip{" +
                "no=" + no +
                ", name='" + name + '\'' +
                ", birth='" + birth + '\'' +
                ", sex=" + sex +
                '}';
    }
}

反射测试类--ReflectTest12

package com.happy.reflection;

import com.happy.bean.Vip;

import java.lang.reflect.Constructor;

public class ReflectTest12 {
    public static void main(String[] args) throws Exception {
        //不使用反射机制创建对象
        Vip v1 = new Vip();
        Vip v2 = new Vip(110,"zhangsan","2001-10-11",true);

        //使用反射机制创建对象
        Class c = Class.forName("com.happy.bean.Vip");
        //这种方式对象实例化会调用无参构造方法
        Object obj = c.newInstance();
        System.out.println(obj);

        //调用有参构造
        //第一步：先获取到这个有参数的构造方法
        Constructor con = c.getDeclaredConstructor(int.class, String.class, String.class, boolean.class);//这里为4个参数的构造方法
        //第二步：调用构造方法new对象
        Object newObj = con.newInstance(110, "jackson", "1990-10-11", true);
        System.out.println(newObj);

        //获取无参构造方法
        Constructor con2 = c.getDeclaredConstructor();
        Object newObj2 = con2.newInstance();
        System.out.println(newObj2);
    }
}

运行结果：

从上面可以看到有2种调用无参构造方法的方式，一种是通过Class类实例调用，一种是反射获取构造方法，构造方法实例化调用。