反射机制

静态VS动态语言

 

 反射的优点和缺点

 

 

package com.wjx.reflection;

/**
 * 什么是反射
 * @author dell
 */
public class Test01 {
    public static void main(String[] args) throws ClassNotFoundException {
        //通过反射来获取类的class对象
        Class c1 = Class.forName("com.wjx.reflection.User");
        System.out.println(c1);
        Class c2 = Class.forName("com.wjx.reflection.User");
        Class c3 = Class.forName("com.wjx.reflection.User");
        Class c4 = Class.forName("com.wjx.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到class对象中
        System.out.println(c2.hashCode());
        System.out.println(c3.hashCode());
        System.out.println(c4.hashCode());
    }
}
//实体类
class User{
    private int id;
    private int age;
    private String name;

    public User() {
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

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

　　

获取Class类的实例

 

 

哪些类型可以有Class对象

 

 

package com.wjx.reflection;


import java.lang.annotation.ElementType;

/**
 * 所有类型的Class
 * @author dell
 */
public class Test04 {
    public static void main(String[] args) {
        Class c1 = Object.class;
        Class c2 = Comparable.class;
        Class c3 = String[].class;
        Class c4 = int[][].class;
        Class c5 = Override.class;
        Class c6 = ElementType.class;
        Class c7 = Integer.class;
        Class c8 = void.class;
        Class c9 = Class.class;

        System.out.println(c1);
        System.out.println(c2);
        System.out.println(c3);
        System.out.println(c4);
        System.out.println(c5);
        System.out.println(c6);
        System.out.println(c7);
        System.out.println(c8);
        System.out.println(c9);
    }
}