是这样 我在Student类中定义了一个私有类SortMethod，它实现了Comparator<Student>接口，覆盖了方法compare（T t1，T  t2），在MainTest测试主类调用Collections.sort（List<T> t,Comparator<T> com）.现在我想在Student类中直接获取该类的一个实例，直接传给MainTest类中Collections.sort（）方法。问题出来了，该如何通过Student类来获取SortMethod的对象。我仿造c#的方法。结果行不通。下面是代码，红色字体部分。望不吝解析，谢谢！！

1. import java.util.Comparator;
   
2. class Student implements Comparable<Student> {
   
3.         private String stuname;
   
4.         private int maths;
   
5.         private int ens;
   
6.         private int phs;
   
7.         private int sum;
   
8.         public Student(){}
   
9.         public Student(String name,int maths,int ens,int phs ) {
   
10.                 this.stuname=name;
    
11.                 this.maths=maths;
    
12.                 this.ens=ens;
    
13.                 this.phs=phs;
    
14.                 sum=maths+ens+phs;
    
15.         }
    
16.         public String getStuName(){
    
17.                 return this.stuname;
    
18.         }
    
19.         public int getSum(){
    
20.                 return this.sum;
    
21.         }
    
22.         public int compareTo(Student stu){
    
23.                 if(this.sum>stu.sum)
    
24.                         return 1;
    
25.                 if(this.sum<stu.sum)
    
26.                         return -1;
    
27.                 else
    
28.                         return 0;
    
29.         }
    
30.         public int hasCode(){
    
31.                 return this.stuname.hashCode()+sum*12;
    
32.         }
    
33.         public boolean equals(Object obj){
    
34.                 if(!(obj instanceof Student))
    
35.                 {
    
36.                         throw new ClassCastException("类型不匹配");
    
37.                 }               
    
38.                 Student student=(Student)obj;
    
39.                 return this.stuname.equals(student.stuname)&&this.sum==student.sum;
    
40.                
    
41.         }
    
42.         public String toString(){
    
43.                 return "学生信息："+this.stuname+"----"+this.sum;
    
44. }
    
45. <font color="red">private class SortMethod implements Comparator<Student>{
    
46.                 public int compare(Student stu1,Student stu2){
    
47.                 return stu1.stuname.compareTo(stu2.stuname);
    
48. }
    
49. <font color="blue">//这是我仿造c#写的获取类SortMethod对象的方法，该行报错
    
50. </font> public static Comparator<Student> getInstance{
    
51.          get{ return new SortMethod();};
    
52. <font color="#0000ff">/*别告诉我这样 public  Comparator<Student> getInstance（）{
    
53.   return new SortMethod()}，这样没法在类外通过Student类名调用*/</font> </font>
    
54. }
    
55. }
    

复制代码

杜鹏云 发表于 2012-8-7 17:10
private  static class SortMethod implements Comparator{//SortMethod 必须声明为静态类，否则不能调用下 ...

我这里的getIntance不是方法 是属性。我想模仿c#中的属性Get方法来获取的！
应该把getInstance()放在Student类，而不是SortMethod类中，要不外界怎么能使用类SortMethod啊！
private  static class SortMethod implements Comparator<Student>{
    public int compare(Student stu1,Student stu2){
           return stu1.stuname.compareTo(stu2.stuname);
         }
}
public static Comparator<Student> getIntance()//方法 getIntance 不能声明为“静态”；只能在静态类型或顶级类型中才能声明静态方法,
    {
    return new SortMethod();
    }

1. import java.util.Comparator;
   
2. 
   
3. class Student implements Comparable<Student> {
   
4. 
   
5. private String stuname;
   
6. 
   
7. private int maths;
   
8. 
   
9. private int ens;
   
10. 
    
11. private int phs;
    
12. 
    
13. private int sum;
    
14. 
    
15. <FONT color=red>public SortMethod sortMethod ;
    
16. public Student(){sortMethod =new SortMethod();}
    
17. 
    
18. public Student(String name,int maths,int ens,int phs ) {
    
19. sortMethod =new SortMethod();
    
20. </FONT>this.stuname=name;
    
21. 
    
22. this.maths=maths;
    
23. 
    
24. this.ens=ens;
    
25. 
    
26. this.phs=phs;
    
27. 
    
28. sum=maths+ens+phs;
    
29. 
    
30. }
    
31. 
    
32. public String getStuName(){
    
33. 
    
34. return this.stuname;
    
35. 
    
36. }
    
37. 
    
38. public int getSum(){
    
39. 
    
40. return this.sum;
    
41. 
    
42. }
    
43. 
    
44. public int compareTo(Student stu){
    
45. 
    
46. if(this.sum>stu.sum)
    
47. 
    
48. return 1;
    
49. 
    
50. if(this.sum<stu.sum)
    
51. 
    
52. return -1;
    
53. 
    
54. else
    
55. 
    
56. return 0;
    
57. 
    
58. }
    
59. 
    
60. public int hasCode(){
    
61. 
    
62. return this.stuname.hashCode()+sum*12;
    
63. 
    
64. }
    
65. 
    
66. public boolean equals(Object obj){
    
67. 
    
68. if(!(obj instanceof Student))
    
69. 
    
70. {
    
71. 
    
72. throw new ClassCastException("类型不匹配");
    
73. 
    
74. }
    
75. 
    
76. Student student=(Student)obj;
    
77. 
    
78. return this.stuname.equals(student.stuname)&&this.sum==student.sum;
    
79. 
    
80. 
    
81. 
    
82. }
    
83. 
    
84. public String toString(){
    
85. 
    
86. return "学生信息："+this.stuname+"----"+this.sum;
    
87. 
    
88. }
    
89. 
    
90. class SortMethod implements Comparator<Student>{
    
91. 
    
92. public int compare(Student stu1,Student stu2){
    
93. 
    
94. return stu1.stuname.compareTo(stu2.stuname);
    
95. 
    
96. }
    
97. }
    
98. }
    
99. 
    
100. 
     

复制代码

private  static class SortMethod implements Comparator<Student>{//SortMethod 必须声明为静态类，否则不能调用下面的静态方法


    public int compare(Student stu1,Student stu2)
    {
       return stu1.stuname.compareTo(stu2.stuname);
    }
   
   
    public static Comparator<Student> getIntance()//方法 getIntance 不能声明为“静态”；只能在静态类型或顶级类型中才能声明静态方法,
    {
             return new SortMethod();
    }
}