HashMap统计字符串出现的个数

Java中HaspMap类的添加元素需要使用key(键值唯一性)和Value内容数据.

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package com.lan;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class MapTest4
{
    public static void main(String[] arg){
        HashMap map = new HashMap();
        int j = 1;
        for(int i = 0; i < arg.length; i++)
        {
            if( null == map.get(arg[i]))
            {
                j = 1;
                map.put(arg[i], String.valueOf(j));
            }
            else
            {
                String strj = (String)map.get(arg[i]); //多态
                j = Integer.valueOf(strj);
                j++;
                map.put(arg[i], String.valueOf(j));
            }
        }
        //System.out.println(map);
        Set sett = map.keySet();
        for(Iterator iter = sett.iterator(); iter.hasNext(); ){
            String key = (String)iter.next(); //多态
            String val = (String)map.get(key);
            System.out.println(key + "出现次数:" + val);
        }
    }

}