java遍历哈希表及其常用方法（附代码）

通过Map.entrySet遍历key和value

Map map = new HashMap();

        for (int i = 0; i < 10; i++) {
            map.put((char) (i + 61), i);
        }

        for (Map.Entry map_1 : map.entrySet()) {
            System.out.println("Key = " + map_1.getKey() + ", Value = " + map_1.getValue());
        }
}  

输出

Key = @, Value = 3
Key = A, Value = 4
Key = B, Value = 5
Key = C, Value = 6
Key = D, Value = 7
Key = E, Value = 8
Key = F, Value = 9
Key = =, Value = 0
Key = >, Value = 1
Key = ?, Value = 2

通过遍历key，通过键找值value

public static void main(String[] args) {
        Map map = new HashMap();
        for (int i = 0; i < 10; i++) {
            map.put((char) (i + 61), i);
        }
        for (char map_2 : map.keySet()){
            System.out.println(map.get(map_2));
        }
    }
 
}

输出

3
4
5
6
7
8
9
0
1
2

在这里插入代码片

如果只需要map中的键或者值，你可以通过Map.keySet或Map.values来实现遍历

public static void main(String[] args) {
        Map map = new HashMap();

        for (int i = 0; i < 10; i++) {
            map.put((char) (i + 61), i);
        }
        for (char map_3 : map.keySet()){
            System.out.println(map_3);
        }
        for (Integer map_4: map.values()) {
            System.out.println(map_4);
        }
}  

通过Map.entrySet使用iterator遍历key和value

public static void main(String[] args) {
        Map map = new HashMap();

        for (int i = 0; i < 10; i++) {
            map.put((char) (i + 61), i);
        }

        Iterator> map_5 = map.entrySet().iterator();

        while (map_5.hasNext()) {
            Map.Entry entry = map_5.next();
            System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
        }
    }
}

输出：

Key = @, Value = 3
Key = A, Value = 4
Key = B, Value = 5
Key = C, Value = 6
Key = D, Value = 7
Key = E, Value = 8
Key = F, Value = 9
Key = =, Value = 0
Key = >, Value = 1
Key = ?, Value = 2

map.getOrDefault(index, default); // 获取索引位置的值，若为null，则为默认值default
map.getKey(); // 获取指定value的key
map.getValue(); // 获取指定key的value
map.keySet(); // 获取哈希表的键值集合
map.values(); // 获取哈希表的值集合