动态创建对象执行方法

有了Class对象，能做什么？

调用指定的方法

setAccessible的作用：

代码如下：

public class Demo10 {
    
    public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException, NoSuchMethodException, InvocationTargetException, NoSuchFieldException {
    
        Class c1 = Class.forName("www.jin.User");

        //构造一个对象
        User user = (User) c1.newInstance();//本质是调用了类的无参构造器
        System.out.println(user);

        System.out.println("-----------------------");
        //通过构造器创建对象
        Constructor constructor = c1.getDeclaredConstructor(String.class, int.class, int.class);
        User user2 = (User) constructor.newInstance("酷小亚",001,14);
        System.out.println(user2);

        //通过反射调用普通方法
        User user3 = (User) c1.newInstance();
        //通过反射获取一个方法
        Method setName = c1.getDeclaredMethod("setName", String.class);

        //invoke : 激活的意思
        //(对象,"方法的值")
        setName.invoke(user3,"今宵");
        System.out.println(user3.getName());

        System.out.println("=======================");
        //通过反射操作属性
        User user4 = (User) c1.newInstance();
        Field name = c1.getDeclaredField("name");

        //不能直接操作私有属性，我们需要关闭程序的安全检测，属性或者方法的setAccessible(true)
        name.setAccessible(true);

        name.set(user4,"晋小");
        System.out.println(user4.getName());
    }
}


class User{
    
    private String name;
    private int id;
    private int age;

    public User() {
    
    }

    public User(String name, int id, int age) {
    
        this.name = name;
        this.id = id;
        this.age = age;
    }

    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;
    }

    public int getAge() {
    
        return age;
    }

    public void setAge(int age) {
    
        this.age = age;
    }

    @Override
    public String toString() {
    
        return "User{" +
                "name='" + name + '\'' +
                ", id=" + id +
                ", age=" + age +
                '}';
    }
}

运行结果：