map的一种遍历方式

 

keySet是键的集合，Set里面的类型即key的类型
entrySet是 键-值 对的集合，Set里面的类型是Map.Entry

1.keySet()

Map map=new HashMap();

Iterator it=map.keySet().iterator();

Object key;

Object value;

while(it.hasNext()){

key=it.next();

value=map.get(key);

System.out.println(key+":"+value);

}

 

2.entrySet()

Map map=new HashMap();

Iterator it=map.entrySet().iterator();

Object key;

Object value;

while(it.hasNext()){

Map.Entry entry = (Map.Entry)it.next();

key=entry.getKey();

value=entry.getValue();

System.out.println(key+"="+value);

}

 

 

HashMap<String,String> map = new HashMap<String,String>();
Iterator<Entry<String, String>> it = map.entrySet().iterator();
while (it.hasNext()) {
Entry<String, String> entry = it.next();
String val = entry.getValue();
String key = entry.getKey();
}

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