1 package day15.lesson2.p;
2
3 import java.lang.reflect.InvocationTargetException;
4 import java.lang.reflect.Method;
5 import java.util.ArrayList;
6
7 /*
8 2.10 反射练习
9
10 2.10.1 案例-越过泛型检查
11 通过反射技术，向一个泛型为Integer的ArrayList集合中添加一些字符串String数据
12 */
13 public class Test1Reflect {
14 public static void main(String[] args) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
15 ArrayList<Integer> arrayList = new ArrayList<>();
16
17 arrayList.add(10);
18 arrayList.add(20);
19 // arrayList.add("hello"); //报错，编译异常 --> 即正常情况下无法在ArrayList<Integer>中添加String数据
20
21 //通过反射可以实现该功能
22 Class<? extends ArrayList> c = arrayList.getClass();
23 Method add = c.getMethod("add", Object.class); //类型为Object-->那么通过反射在arrayList添加啥类型数据都行了QAQ
24 //反射可以越过泛型检查，获取到原始方法所需的参数类型
25 add.invoke(arrayList, "hello");
26 add.invoke(arrayList, "world");
27 add.invoke(arrayList, "java");
28
29 System.out.println(arrayList); //[10, 20, hello, world, java]
30 }
31 }
1 package day15.lesson2.p;
2
3 public class Student {
4 public void study(){
5 System.out.println("好好学习天天向上");
6 }
7 }
1 package day15.lesson2.p;
2
3 public class Teacher {
4 public void teach(){
5 System.out.println("好好教书");
6 }
7 }
1 package day15.lesson2.p;
2
3 import java.io.FileNotFoundException;
4 import java.io.FileReader;
5 import java.io.IOException;
6 import java.lang.reflect.Constructor;
7 import java.lang.reflect.InvocationTargetException;
8 import java.lang.reflect.Method;
9 import java.util.Properties;
10
11 /*
12 2.10.2 案例-运行配置文件中指定类的指定方法
13 */
14 public class Test2Reflect {
15 public static void main(String[] args) throws IOException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InstantiationException, InvocationTargetException {
16 /*Student student = new Student();
17 student.study(); //好好学习天天向上
18 Teacher teacher = new Teacher();
19 teacher.teach(); //好好教书*/
20
21 /*
22 自定义配置文件
23 class.txt
24 className=xxx (注意此处类名应为带包全路径)
25 methodName=xxx
26 */
27 Properties properties = new Properties();
28 FileReader fr = new FileReader("stage2\\src\\day15\\lesson2\\p\\class.txt");
29 properties.load(fr);
30 fr.close();
31 System.out.println(properties); //{methodName=study, className=day15.lesson2.p.Student}
32
33 String className = properties.getProperty("className");
34 String methodName = properties.getProperty("methodName");
35 System.out.println(className + "," + methodName); //day15.lesson2.p.Student,study
36
37 //通过反射使用 从配置文件中获取的配置信息
38 Class<?> c = Class.forName(className);
39 Constructor<?> con = c.getConstructor();
40 Object obj = c.newInstance();
41 Method method = c.getMethod(methodName);
42 method.invoke(obj);
43 /*
44 className=day15.lesson2.p.Student
45 methodName=study
46 --> 好好学习天天向上
47
48 className=day15.lesson2.p.Teacher
49 methodName=teach
50 --> 好好教书
51 */
52 }
53 }
className=day15.lesson2.p.Teacher
methodName=teach
