Map集合循环遍历

Map<String, Object> map = new HashMap<String, Object>() {
        {
            put("aaa", 111);
            put("bbb", 222);
            put("ccc", 333);
            put("ddd", 444);
        }
      };

循环遍历key

for(String key:map.keySet()){//keySet获取map集合key的集合  然后在遍历key即可
    String value = map.get(key).toString();//
    System.out.println("key:"+key+" vlaue:"+value);
}

遍历所有的value 无法获取key

 for(Object m:map.values()){
  System.out.println(m);
}

迭代器

Iterator<Entry<String, Object>> it = map.entrySet().iterator();
while(it.hasNext()){
    Entry<String, Object> entry = it.next();
    System.out.println("key:"+entry.getKey()+"  key:"+entry.getValue());
}

循环遍历大容量map

for (Map.Entry<String, Object> m : map.entrySet()) {
    System.out.println("key:" + m.getKey() + " value:" + m.getValue());
}