遍历map和list（自己用）

遍历map

1.这是最常见的并且在大多数情况下也是最可取的遍历方式。在键值都需要时使用。

Map<Integer, Integer> map = new HashMap<Integer, Integer>();  for (Map.Entry<Integer, Integer> entry : map.entrySet()) {    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());  } 

2.在for-each循环中遍历keys或values。

Map<Integer, Integer> map = new HashMap<Integer, Integer>();  //遍历map中的键  for (Integer key : map.keySet()) {    System.out.println("Key = " + key);  }  //遍历map中的值  for (Integer value : map.values()) {    System.out.println("Value = " + value);  } 

3.用迭代器迭代

Map<Integer, Integer> map = new HashMap<Integer, Integer>();  Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator();  while (entries.hasNext()) {    Map.Entry<Integer, Integer> entry = entries.next();    System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());  } 

4.通过键找值遍历（效率低）

Map<Integer, Integer> map = new HashMap<Integer, Integer>();  for (Integer key : map.keySet()) {    Integer value = map.get(key);    System.out.println("Key = " + key + ", Value = " + value); 

遍历list

1.超级for循环遍历

for(String attribute : list) {   System.out.println(attribute); } 

2.对于ArrayList来说速度比较快, 用for循环, 以size为条件遍历

for(int i = 0 ; i < list.size() ; i++) {   system.out.println(list.get(i)); } 

3.用迭代器迭代

Iterator it = list.iterator(); while(it.hasNext()) {   System.ou.println(it.next); } 

文章来源: https://blog.csdn.net/zx19930309/article/details/90202170