HashMap的几种遍历方式

Posted 2020-11-10 chongxinchufa

一、entrySet  键-值对集合

1、iterator

Iterator item = tempMap.entrySet().iterator();
while (item.hasNext()){
        Map.Entry entry = (Map.Entry)item.next();
        String key = entry.getKey().toString();
        Integer value =(Integer)entry.getValue();
        System.out.println("key:"+key+";value:"+value);
}

2、for each

for (Map.Entry<String,Integer> entry : tempMap.entrySet()){
            String key = entry.getKey().toString();
            Integer value =(Integer)entry.getValue();
            System.out.println("key:"+key+";value:"+value);
}

二、keySet  键的集合

1、iterator

Iterator i = tempMap.keySet().iterator();
while (i.hasNext()){
        Object obj = i.next();
        String key = obj.toString();
        Integer value =tempMap.get(key);
        System.out.println("key:"+key+";value:"+value);
}

2、for each

for ( Object obj: tempMap.keySet()){
            String key = obj.toString();
            Integer value =tempMap.get(key);
            System.out.println("key:"+key+";value:"+value);
}

三、lambda表达式

tempMap.forEach((k, v)->{
            System.out.println("key:"+k+";value:"+v);
});