html pri new rgs bject put hashmap 字符 com

一、Map遍歷的4中方法

public static void main(String[] args) {

Map<String, String> map = new HashMap<String, String>();
map.put("1", "value1");
map.put("2", "value2");
map.put("3", "value3");

//第一種：普遍使用，二次取值
System.out.println("通過Map.keySet遍歷key和value：");
for (String key : map.keySet()) {

System.out.println("key= "+ key + " and value= " + map.get(key));
}

//第二種
System.out.println("通過Map.entrySet使用iterator遍歷key和value：");
Iterator<Map.Entry<String, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Map.Entry<String, String> entry = it.next();
System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
}

//第三種：推薦，尤其是容量大時
System.out.println("通過Map.entrySet遍歷key和value");
for (Map.Entry<String, String> entry : map.entrySet()) {
System.out.println("key= " + entry.getKey() + " and value= " + entry.getValue());
}

//第四種
System.out.println("通過Map.values()遍歷所有的value，但不能遍歷key");
for (String v : map.values()) {

System.out.println("value= " + v);
}
}

二、統計字符串中字符的個數

public static void main(String[] args) {
        StringBuilder str=new StringBuilder("aaaaaabbbajjsjjjjj");
        Map<Object,Integer> map=new HashMap<Object,Integer>();
        for(int i=0;i<str.length();i++){
            char t=str.charAt(i);
            int count=0;
            if(map.get(t)==null){
                
                for(int j=i+1;j<str.length();j++){
                    if(t==str.charAt(j)){
                        count++;
                    }
                }
                map.put(t, ++count);
            }
            
        
        }
        for (Object key : map.keySet()) {
               System.out.println("key= "+ key + " and value= " + map.get(key));
        }
    }

轉自：http://www.cnblogs.com/kristain/articles/2033566.html

Map的遍歷方法及字符計數