对字符串中字符出现的次数进行排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 *  对字符串中字符出现的次数进行排序。
 * 
 * @author 赵学庆 www.java2000.net
 */
public class T {
  public static void main(String args[]) {
    String str = "12345678hfdjkslahfkj932189oiefsjkar94werfdsf";
    Map<Character, KeyValue> map = new HashMap<Character, KeyValue>();
    char c;
    KeyValue kv = null;
    for (int i = 0; i < str.length(); i++) {
      c = str.charAt(i);
      kv = map.get(c);
      if (kv == null) {
        kv = new KeyValue();
        kv.ch = c;
        kv.count = 1;
        map.put(c, kv);
      } else {
        kv.count++;
      }
    }
    List<KeyValue> list = new ArrayList<KeyValue>(map.values());
    Collections.sort(list);
    for (KeyValue o : list) {
      System.out.println(o.ch + "=" + o.count);
    }
  }
}

class KeyValue implements Comparable {
  public int compareTo(Object obj) {
    if (obj instanceof KeyValue) {
      KeyValue kv = (KeyValue) obj;
      return kv.count - this.count;
    }
    return -1;
  }

  char ch;

  int count;
}

 运行结果

f=5
j=3
k=3
s=3
9=3
d=2
e=2
a=2
h=2
3=2
2=2
1=2
r=2
4=2
8=2
o=1
l=1
i=1
w=1
7=1
6=1
5=1