1. import java.lang.reflect.Field;
   
2. 
   
3. public class Test9{
   
4. 
   
5. public final int x = 100;
   
6. 
   
7. public int Method(Test9 t1,Test9 t2) throws Exception{
   
8. 
   
9. int i = t1.x;
   
10. 
    
11. System.out.println("i's value is "+i);
    
12. 
    
13. changeX(t1);
    
14. System.out.println("i2's value is "+t1.x);
    
15. 
    
16. int j = t2.x;
    
17. 
    
18. System.out.println("j's value is "+j);
    
19. 
    
20. return j - i;
    
21. 
    
22. }
    
23. 
    
24. public static void changeX(Test9 t1) throws Exception{
    
25. 
    
26. Class clazz = t1.getClass();
    
27. 
    
28. Field fieldX = clazz.getDeclaredField("x");
    
29. 
    
30. fieldX.setAccessible(true);
    
31. 
    
32. fieldX.setInt(t1, 300);
    
33. 
    
34. System.out.println("fieldX's vlaue is "+fieldX.getInt(t1));
    
35. 
    
36. }
    
37. 
    
38. public int test() throws Exception{
    
39. 
    
40. return Method(this,this);
    
41. 
    
42. }
    
43. 
    
44. public static void main(String[] args) throws Exception{
    
45. 
    
46. Test9 t1 = new Test9();
    
47. 
    
48. System.out.println(t1.test());
    
49. 
    
50. }
    
51. 
    
52. }

复制代码

结果是
i's value is 100

fieldX's vlaue is 300

i2's value is 100

j's value is 100

0

1. import java.lang.reflect.Field;
   
2. 
   
3. public class Test9{
   
4. 
   
5. public final int x;
   
6. public Test9()
   
7. {
   
8. x = 100;
   
9. }
   
10. 
    
11. public int Method(Test9 t1,Test9 t2) throws Exception{
    
12. 
    
13. int i = t1.x;
    
14. 
    
15. System.out.println("i's value is "+i);
    
16. 
    
17. changeX(t1);
    
18. System.out.println("i2's value is "+t1.x);
    
19. 
    
20. int j = t2.x;
    
21. 
    
22. System.out.println("j's value is "+j);
    
23. 
    
24. return j - i;
    
25. 
    
26. }
    
27. 
    
28. public static void changeX(Test9 t1) throws Exception{
    
29. 
    
30. Class clazz = t1.getClass();
    
31. 
    
32. Field fieldX = clazz.getDeclaredField("x");
    
33. 
    
34. fieldX.setAccessible(true);
    
35. 
    
36. fieldX.setInt(t1, 300);
    
37. 
    
38. System.out.println("fieldX's vlaue is "+fieldX.getInt(t1));
    
39. 
    
40. }
    
41. 
    
42. public int test() throws Exception{
    
43. 
    
44. return Method(this,this);
    
45. 
    
46. }
    
47. 
    
48. public static void main(String[] args) throws Exception{
    
49. 
    
50. Test9 t1 = new Test9();
    
51. 
    
52. System.out.println(t1.test());
    
53. 
    
54. 
    
55. 
    
56. }
    
57. 
    
58. }
    
59. 
    
60. 
    

复制代码

结果是
i's value is 100
fieldX's vlaue is 300
i2's value is 300
j's value is 300
200


为什么两种情况不一样？

难道是用记事本打的？头都看昏了，麻烦你排下版。。。这太不规范了。

import java.lang.reflect.*;
public class Test9{

public final int x;

public Test9()

{

x = 100;

}
//输出两对象相减的结果

public int Method(Test9 t1,Test9 t2) throws Exception{

int i = t1.x;
//此时i为100
System.out.println("i's value is "+i);

changeX(t1); //调用方法后t1.x为300

System.out.println("i2's value is "+t1.x);

int j = t2.x;//j为300,this代表t1

System.out.println("j's value is "+j);

return j - i; //300-100

}
//更改对象属性值
public static void changeX(Test9 t1) throws Exception{

Class clazz = t1.getClass();

Field fieldX = clazz.getDeclaredField("x");

fieldX.setAccessible(true);

fieldX.setInt(t1, 300);

System.out.println("fieldX's vlaue is "+fieldX.getInt(t1));

}

public int test() throws Exception{

return Method(this,this);

}

public static void main(String[] args) throws Exception{

Test9 t1 = new Test9();

System.out.println(t1.test());

}

}


/*运行结果是：

i's value is 100

fieldX's vlaue is 300

i2's value is 300

j's value is 300

200*/
//this代表同一对象

参照这思路解决第二个！

tianyun 发表于 2013-3-14 18:09
参照这思路解决第二个！

???？
第一种情况 用反射最终没改变x的值
第二种情况 却改变成功了
为什么

{:soso_e127:}还没人回答问题呢。上面的答案莫名奇妙，乱写一通