java虚拟机：01_类加载器和反射

1. 定义接口

package com.guoyasoft;

public interface IStudy {
    public boolean doHomeWork(String renwu);
    public int learn(String course);
}

2. 写检查代码

package com.guoyasoft;

import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;

public class TestIStudy {
    public static void main(String[] args) {
        try {
            // 第1步：分派任务
            Map task = new HashMap();
            task.put("wuhao", "com.guoyasoft.StudentWH");
            task.put("chenyuan", "com.guoyasoft.StudentCH");

            String wuhaoClass = (String) task.get("wuhao");
            //手动将需要的class类加载到虚拟机内存，返回class对象（类型对象） 
            Class classWuhao = Class.forName(wuhaoClass);
            //newInstance()调用类的无参构造器，生成一个实例对象，等价于new 对象名()
            IStudy wuhao = (IStudy) classWuhao.newInstance();
            
            boolean isDone = wuhao.doHomeWork("抄10遍");
            int score = wuhao.learn("法语");
            System.out.println("isDone homework=" + isDone + "; 法语成绩：" + score);
            
            String chenyuanClass = (String) task.get("chenyuan");
            Class classChenyuan = Class.forName(wuhaoClass);
            IStudy chenyuan = (IStudy) classWuhao.newInstance();
            isDone = wuhao.doHomeWork("抄10遍");
            score = wuhao.learn("法语");
            System.out.println("isDone homework=" + isDone + "; 法语成绩：" + score);
            
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

3. 任务提交前测试

执行TestIStudy

java.lang.ClassNotFoundException: com.guoyasoft.StudentWH1
    at java.net.URLClassLoader$1.run(URLClassLoader.java:366)
    at java.net.URLClassLoader$1.run(URLClassLoader.java:355)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:354)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:308)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:190)
    at com.guoyasoft.TestIStudy.main(TestIStudy.java:17)

4. 实现接口

提交作业1

package com.guoyasoft;

public class StudentWH implements IStudy{

    @Override
    public boolean doHomeWork(String renwu) {
        System.out.println("开始做作业");
        System.out.println("开始看手机");
        System.out.println("开始玩游戏");
        System.out.println("不做了");
        return false;
    }

    @Override
    public int learn(String course) {
        System.out.println("不想学");
        return 0;
    }

}

提交作业2

package com.guoyasoft;

public class StudentCH implements IStudy {

    @Override
    public boolean doHomeWork(String renwu) {
        System.out.println("游戏");
        System.out.println("代做");
        return true;
    }

    @Override
    public int learn(String course) {
        System.out.println("我喜欢");
        return 90;
    }

}

5. 提交代码后测试

运行TestIStudy类

开始做作业
开始看手机
开始玩游戏
不做了
不想学
isDone homework=false; 法语成绩：0
游戏
代做
我喜欢
isDone homework=true; 法语成绩：90

6. 面向接口编程的思想

使用接口，将各种各样类型的类抽象成同一种更高层级的类型，然后当作同一种类型进行批量处理