TreeMap hm = new TreeMap<String, String>(new Comparator() {
    public int compare(Object o1, Object o2) {
       //如果有空值，直接返回0
       if (o1 == null || o2 == null)
         return 0;
       return String.valueOf(o1).compareTo(String.valueOf(o2));
    }
});

TreeMap hm = new TreeMap<String, String>(new Comparator() {
     public int compare(Object o1, Object o2) {
        //如果有空值，直接返回0
        if (o1 == null || o2 == null)
           return 0;
       CollationKey ck1 = collator.getCollationKey(String.valueOf(o1));
       CollationKey ck2 = collator.getCollationKey(String.valueOf(o2));
       return ck1.compareTo(ck2);
    }
});

package ChineseSort;
import java.util.Collection;
import java.util.Iterator;
import java.util.SortedMap;
import java.util.TreeMap;
public class TestSort {
public static void main(String[] args) {
  // TODO Auto-generated method stub
  CollatorComparator comparator = new CollatorComparator();
  TreeMap map = new TreeMap(comparator);
  for(int i=0; i<10; i++) {
    String s = ""+(int)(Math.random()*1000);
    map.put(s,s);
  }
  map.put("abcd","abcd");
  map.put("Abc", "Abc");
  map.put("bbb","bbb");
  map.put("BBBB", "BBBB");
  map.put("北京","北京");
  map.put("中国","中国");
  map.put("上海", "上海");
  map.put("厦门", "厦门");
  map.put("香港", "香港");
  map.put("碑海", "碑海");
  Collection col = map.values();
  Iterator it = col.iterator();
  while(it.hasNext()) {
    System.out.println(it.next());
  }
}
}

package ChineseSort;
import java.text.CollationKey;
import java.text.Collator;
import java.util.Comparator;
public class CollatorComparator implements Comparator {
Collator collator = Collator.getInstance();
public int compare(Object element1, Object element2) {
  CollationKey key1 = collator.getCollationKey(element1.toString());
  CollationKey key2 = collator.getCollationKey(element2.toString());
  return key1.compareTo(key2);
}
}

325
62
653
72
730
757
874
895
909
921
Abc
abcd
bbb
BBBB
碑海
北京
上海
厦门
香港
中国

element1.toString()

element1.toString().toLowerCase()

element2.toString()

element2.toString().toLowerCase()