1、 在for-each循环中使用entries来遍历

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、使用Iterator遍历

1)

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());

2)不使用泛型：

Map map = new HashMap();  

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

while (entries.hasNext()) {  

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

    Integer key = (Integer)entry.getKey();  

    Integer value = (Integer)entry.getValue();  

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

}

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);  

}