# Java - 從`HashMap`獲取鍵集視圖 > 原文： [https://beginnersbook.com/2014/08/java-get-set-view-of-keys-from-hashmap/](https://beginnersbook.com/2014/08/java-get-set-view-of-keys-from-hashmap/) #### 描述 程序從`HashMap`獲取鍵集。 #### 示例 ```java import java.util.Iterator; import java.util.HashMap; import java.util.Set; class HashMapExample{ public static void main(String args[]) { // Create a HashMap HashMap<String, String> hmap = new HashMap<String, String>(); // Adding few elements hmap.put("Key1", "Jack"); hmap.put("Key2", "Rock"); hmap.put("Key3", "Rick"); hmap.put("Key4", "Smith"); hmap.put("Key5", "Will"); // Getting Set of HashMap keys /* public Set<K> keySet(): Returns a Set view of the keys contained * in this map. The set is backed by the map, so changes to the map * are reflected in the set, and vice-versa. */ Set<String> keys = hmap.keySet(); System.out.println("Set of Keys contains: "); /* If your HashMap has integer keys then specify the iterator like * this: Iterator<Integer> it = keys.iterator(); */ Iterator<String> it = keys.iterator(); // Displaying keys. Output will not be in any particular order while(it.hasNext()){ System.out.println(it.next()); } } } ``` **輸出：** ```java Set of Keys contains: Key2 Key1 Key4 Key3 Key5 ``` 注意：這組鍵由原始`HashMap`備份，因此如果從`Set`中刪除任何鍵，它將自動從`HashMap`中刪除。