Java String类中CaseInsensitiveComparator.compare()方法的实现

String对象的大小写不敏感比较方法的实现如下：

 1         public int compare(String s1, String s2) {

 2             int n1 = s1.length();

 3             int n2 = s2.length();

 4             int min = Math.min(n1, n2);

 5             for (int i = 0; i < min; i++) {

 6                 char c1 = s1.charAt(i);

 7                 char c2 = s2.charAt(i);

 8                 if (c1 != c2) {

 9                     c1 = Character.toUpperCase(c1);

10                     c2 = Character.toUpperCase(c2);

11                     if (c1 != c2) {

12                         c1 = Character.toLowerCase(c1);

13                         c2 = Character.toLowerCase(c2);

14                         if (c1 != c2) {

15                             // No overflow because of numeric promotion

16                             return c1 - c2;

17                         }

18                     }

19                 }

20             }

21             return n1 - n2;

22         }

这里，同时比较了UpperCase和LowerCase，是为了兼容Georgian字符。

见String类的regionMatches()方法。如下(29~32行)：

 1     public boolean regionMatches(boolean ignoreCase, int toffset,

 2             String other, int ooffset, int len) {

 3         char ta[] = value;

 4         int to = toffset;

 5         char pa[] = other.value;

 6         int po = ooffset;

 7         // Note: toffset, ooffset, or len might be near -1>>>1.

 8         if ((ooffset < 0) || (toffset < 0)

 9                 || (toffset > (long)value.length - len)

10                 || (ooffset > (long)other.value.length - len)) {

11             return false;

12         }

13         while (len-- > 0) {

14             char c1 = ta[to++];

15             char c2 = pa[po++];

16             if (c1 == c2) {

17                 continue;

18             }

19             if (ignoreCase) {

20                 // If characters don't match but case may be ignored,

21                 // try converting both characters to uppercase.

22                 // If the results match, then the comparison scan should

23                 // continue.

24                 char u1 = Character.toUpperCase(c1);

25                 char u2 = Character.toUpperCase(c2);

26                 if (u1 == u2) {

27                     continue;

28                 }

29                 // Unfortunately, conversion to uppercase does not work properly

30                 // for the Georgian alphabet, which has strange rules about case

31                 // conversion.  So we need to make one last check before

32                 // exiting.

33                 if (Character.toLowerCase(u1) == Character.toLowerCase(u2)) {

34                     continue;

35                 }

36             }

37             return false;

38         }

39         return true;

40     }