使用map集合统计字符串中字母出现的次数

import java.util.Comparator;

import java.util.Iterator;

import java.util.Map;

import java.util.Set;

import java.util.TreeMap;

public class MapTest implements Comparator <Character>{

/**

* @param args

*/

@Override

public int compare(Character o1, Character o2) {

// TODO Auto-generated method stub

return o1-o2;

}

public MapTest() {

super();

// TODO Auto-generated constructor stub

}

public static void main(String[] args) {

// TODO Auto-generated method stub

String str="fdgavcbsacdfs";

TreeMap <Character,Integer> hm=new TreeMap <Character,Integer>(new MapTest());

hm=toMap(str);

Set <Map.Entry<Character,Integer>> set=hm.entrySet();

Iterator <Map.Entry<Character,Integer>> it=set.iterator();

while(it.hasNext())

{

Map.Entry<Character,Integer> m=it.next();

System.out.print(m.getKey()+"("+m.getValue()+")");

}

}

public static TreeMap toMap(String str)

{

char [] ch=str.toCharArray();

TreeMap <Character,Integer> hm=new TreeMap <Character,Integer>();

for (int i = 0; i < ch.length; i++) {

if(hm.containsKey(ch[i]))

{

Integer in=hm.get(ch[i]);

in=in+1;

hm.put(ch[i], in);

}

else hm.put(ch[i], 1);

}

return hm;

}

}