反射概念

package reflection;
//什么叫反射
public class Test01 extends Object{
    public static void main(String[] args) throws ClassNotFoundException {
         //通过反射获取类的Class对象
        Class c1 = Class.forName("reflection.User");
        System.out.println(c1);

        Class c2 = Class.forName("reflection.User");
        Class c3 = Class.forName("reflection.User");
        Class c4 = Class.forName("reflection.User");

        //一个类在内存中只有一个class对象
        //一个类被加载后，类的整个结构都会被封装在Class对象中，也就是反射对象中
        //若hashcode一样，说明是同一个类
        System.out.println(c2.hashCode());
        System.out.println(c3.hashCode());
        System.out.println(c4.hashCode());
    }
}

//实体类：如果类中只有属性，就叫做实体类

//创建一个实体类
class User{
    private String name;
    private int id;
    private int age;
    //首先要有无参构造
    public User() {
    }
    //有参构造
    public User(String name, int id, int age) {
        this.name = name;//这些属性会与数据库映射
        this.id = id;
        this.age = age;
    }
    //Alt+ins：生成get和set方法
    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;
    }
    //alt+ins生成tostring方法，方便写程序时去调试
    @Override
    public String toString() {
        return "User{" +
                "name='" + name + '\'' +
                ", id=" + id +
                ", age=" + age +
                '}';
    }
}