从一个英文字符串中找出每个单词出现的频率

import java.util.*;

public class Lookup{
    public static void main(String[] args){
        String s = "the instruction set of the Java virtual machine distinguishes its operand types using instructions intended to operate on values of specific types";
        String[] word = s.split(" ");
        Map<String,Integer> m = new HashMap<String,Integer>();
        //用word初使化m，m中包含了所有不重复的单词
        for(int j=0;j<word.length;j++){
            m.put(word[j],0);
        }
        
        Set<String> set = m.keySet(); 
        //用word中的每个单词与m中的单词比较，发现相同的就统计一次    
        for(int i=0;i<word.length;i++){
        Iterator<String> it = set.iterator();
         while(it.hasNext()){
              String k = it.next();
              if(word[i].equals(k)){
                    int c = m.get(k);                  
                    c++;
                    m.put(word[i],c);
                }
            }                          
        }
        System.out.println(m);
    }
}