HashMap一共有四种遍历方式。

Key和Value

• 使用Iterator进行遍历

    public static void printHashMap1(HashMap<Integer, Integer> hashMap) {
        Iterator<Map.Entry<Integer, Integer>> iterator = hashMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, Integer> entry = iterator.next();
            System.out.print(entry.getKey());
            System.out.println(entry.getValue());
        }
    }

• 直接使用For循环进行遍历

    public static void printHashMap2(HashMap<Integer, Integer> hashMap) {
        for (Map.Entry<Integer, Integer> entry : hashMap.entrySet()){
            System.out.print(entry.getKey());
            System.out.println(entry.getValue());
        }
    }

• 通过key进行遍历所有的值

    public static void printHashMap3(HashMap<Integer, Integer> hashMap) {
        for (Integer key : hashMap.keySet()){
            System.out.print(key);
            System.out.println(hashMap.get(key));
        }
    }

Value

• 遍历获取所有的Value

    public static void printHashMap4(HashMap<Integer, Integer> hashMap) {
        for (Integer value : hashMap.values()){
            System.out.print(value);
        }
    }

更新HashMap，删除某个Key

    public static void removeHashMap(HashMap<Integer, Integer> hashMap) {
        Iterator<Map.Entry<Integer, Integer>> iterator = hashMap.entrySet().iterator();
        while (iterator.hasNext()) {
            Map.Entry<Integer, Integer> entry = iterator.next();
            iterator.remove();
            System.out.print(entry.getKey());
            System.out.println(entry.getValue());
        }
    }