Java 反射

反射（reflection）: 在多个类没有公共特性时，

                    可以在一个基类方法中，

                    通过反射，

                    实现对这些没有公共特性的类的普遍性调用。

 

一：class.getmethod()

　　①//getmethod(string name, class<?>... parametertypes)

 　　      method method = class.getmethod("要调用的方法名称","要调用的方法的形参的类型的class");

    ②//invoke(object obj, object... args)

　　  method.invoke("对象实例","要调用的方法的形参");

 1 public class reflectivetest {
 2 
 3     public static void reflectivemethod(object object) {
 4 
 5         system.out.println("-------------反射使用方法--------------");
 6 
 7         class<?> clazz = object.getclass();
 8         try {
 9 
10             //getmethod():第一个参数方法名称；第二个参数：方法的形参的class
11             method sitmethod = clazz.getmethod("sit",null);
12             sitmethod.invoke(object,null);
13         } catch (nosuchmethodexception | illegalaccessexception | invocationtargetexception e) {
14             e.printstacktrace();
15         }
16 
17 
18         try {
19             method eatmethod = clazz.getmethod("eat",string.class);
20             eatmethod.invoke(object,"pork");
21         } catch (nosuchmethodexception | illegalaccessexception | invocationtargetexception e) {
22             e.printstacktrace();
23         }
24 
25         try {
26 
27             method calculatemethod = clazz.getmethod("calculate",int.class,int.class);
28             int a = (integer) calculatemethod.invoke(object,1024,2048);
29             system.out.println("calculatemethod 结果=" + a);
30         } catch (nosuchmethodexception | illegalaccessexception | invocationtargetexception e) {
31             e.printstacktrace();
32         }
33 
34     }
35 
36 
37     public static void main(string[] args) {
38 
39         dog dog = new dog();
40         robot robot = new robot();
41 
42         reflectivemethod(dog);
43         reflectivemethod(robot);
44     }
45 
46 
47 }

运行结果：

 1 -----------------反射使用方法-------------------
 2 dog sits 
 3 dog eats pork
 4 java.lang.nosuchmethodexception: com.wing.test.vo.dog.calculate(int, int)
 5     at java.lang.class.getmethod(class.java:1786)
 6     at com.wing.test.reflectivetest.reflectivemethod(reflectivetest.java:41)
 7     at com.wing.test.reflectivetest.main(reflectivetest.java:56)
 8 java.lang.nosuchmethodexception: com.wing.test.vo.robot.eat(java.lang.string)
 9     at java.lang.class.getmethod(class.java:1786)
10     at com.wing.test.reflectivetest.reflectivemethod(reflectivetest.java:33)
11     at com.wing.test.reflectivetest.main(reflectivetest.java:57)
12 -----------------反射使用方法-------------------
13 robot sits
14 robot calculates a + b = 3072
15 calculatemethod 结果=3072

 

辅助类：

 1 public class dog {
 2 
 3     public dog() {
 4     }
 5 
 6     public void sit(){
 7         system.out.println("dog sits ");
 8     }
 9 
10     public void eat(string meat){
11         system.out.println("dog eats " + meat);
12     }
13 
14 
15 }
16 
17 
18 public class robot {
19 
20     public robot() {
21     }
22 
23     public void sit(){
24         system.out.println("robot sits");
25     }
26 
27     public int calculate(int a,int b){
28         int c = a + b;
29         system.out.println("robot calculates a + b = " + c);
30         return c;
31     }
32 
33 }