通过反射创建对象和调用方法

//reflect.User表示User类的全路径

User user = (User) Class.forName("reflect.User").newInstance();   

//getConstructor(String.class,String.class)表示该构造方法有两个参数，参数类型为String
//newInstance("张三","20") :给参数赋值

User user1=(User) Class.forName("reflect.User").getConstructor(String.class,String.class).newInstance("张三","20");

Method method = user.getClass().getMethod("sayHello", String.class); //“sayHello方法名”
method.invoke(user, "张三");  //给方法参数赋值

package reflect;

import java.lang.reflect.Method;

public class demo1 {
    public static void main(String[] args) {
        try {
            User user = (User) Class.forName("reflect.User").newInstance();
            User user1=(User) Class.forName("reflect.User").getConstructor(String.class,String.class).newInstance("张三","20");
            System.out.println(user);
            System.out.println(user1);
            //通过对象反射方法
            Method method = user.getClass().getMethod("sayHello", String.class);
            method.invoke(user, "张三");
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

class User{
    private String name;
    private String age;
    public User(){}
    public User(String name,String age) {
        this.name = name;
        this.age = age;
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + "]";
    }
    
    public void sayHello(String name) {
        System.out.println("Hello "+name);
    }
    
}