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                # Java - 檢查`HashMap`中是否存在特定鍵 > 原文: [https://beginnersbook.com/2014/07/java-check-if-a-particular-key-exists-in-hashmap-example/](https://beginnersbook.com/2014/07/java-check-if-a-particular-key-exists-in-hashmap-example/) 在上一個教程中,我們學習了如何[檢查`HashMap`](https://beginnersbook.com/2014/07/java-check-if-a-particular-value-exists-in-hashmap-example/) 中是否存在特定值。在這個例子中,我們將看看如何檢查`HashMap`中是否存在特定的鍵。我們將使用`HashMap`類的[`containsKey()`](https://docs.oracle.com/javase/7/docs/api/java/util/HashMap.html#containsKey(java.lang.Object))方法來執行此檢查。方法定義和描述如下: `public boolean containsKey(Object key)`:如果此映射包含指定鍵的映射,則返回`true`。 #### 示例 我們在以下示例中遵循的步驟是: 1)創建一個`HashMap`并用鍵值對填充它。 2)通過調用`containsKey()`方法檢查任何鍵存在。此方法返回一個布爾值。 ```java import java.util.HashMap; public class CheckKeyExample { public static void main(String[] args) { // Creating a HashMap of int keys and String values HashMap<Integer, String> hashmap = new HashMap<Integer, String>(); // Adding Key and Value pairs to HashMap hashmap.put(11,"Chaitanya"); hashmap.put(22,"Pratap"); hashmap.put(33,"Singh"); hashmap.put(44,"Rajesh"); hashmap.put(55,"Kate"); // Checking Key Existence boolean flag = hashmap.containsKey(22); System.out.println("Key 22 exists in HashMap? : " + flag); boolean flag2 = hashmap.containsKey(55); System.out.println("Key 55 exists in HashMap? : " + flag2); boolean flag3 = hashmap.containsKey(99); System.out.println("Key 99 exists in HashMap? : " + flag3); } } ``` **輸出:** ```java Key 22 exists in HashMap? : true Key 55 exists in HashMap? : true Key 99 exists in HashMap? : false ```
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