Java LinkedHashMap containsKey()用法及代碼示例

java.util.LinkedHashMap.containsKey() 方法用於檢查特定鍵是否映射到LinkedHashMap 中。它將關鍵元素作為參數，如果該元素已映射到映射中，則返回 True。
用法:

Linked_Hash_Map.containsKey(key_element)

參數：該方法隻需要一個參數key_element它指的是應該在映射內檢查其映射的鍵。

返回類型：如果檢測到 key 存在，該方法返回布爾值 true，否則返回 false。

示例 1：將字符串值映射到整數鍵。

Java


// Java code to illustrate the containsKey() method 
import java.util.*; 
  
public class Linked_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty LinkedHashMap 
        LinkedHashMap<Integer, String> li_hash_map =  
        new LinkedHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        li_hash_map.put(10, "Geeks"); 
        li_hash_map.put(15, "4"); 
        li_hash_map.put(20, "Geeks"); 
        li_hash_map.put(25, "Welcomes"); 
        li_hash_map.put(30, "You"); 
  
        // Displaying the LinkedHashMap 
        System.out.println("Initial Mappings are: " + li_hash_map); 
  
        // Checking for the key_element '20' 
        System.out.println("Is the key '20' present? " +  
        li_hash_map.containsKey(20)); 
  
        // Checking for the key_element '5' 
        System.out.println("Is the key '5' present? " +  
        li_hash_map.containsKey(5)); 
    } 
}

輸出：

Initial Mappings are: {10=Geeks, 15=4, 20=Geeks, 25=Welcomes, 30=You}
Is the key '20' present? true
Is the key '5' present? false

示例 2：將整數值映射到字符串鍵。

Java


// Java code to illustrate the containsKey() method 
import java.util.*; 
  
public class Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty LinkedHashMap 
        LinkedHashMap<String, Integer> li_hash_map =  
        new LinkedHashMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        li_hash_map.put("Geeks", 10); 
        li_hash_map.put("4", 15); 
        li_hash_map.put("Geeks", 20); 
        li_hash_map.put("Welcomes", 25); 
        li_hash_map.put("You", 30); 
  
        // Displaying the LinkedHashMapHashMap 
        System.out.println("Initial Mappings are: " + li_hash_map); 
  
        // Checking for the key_element 'Welcomes' 
        System.out.println("Is the key 'Welcomes' present? " +  
        li_hash_map.containsKey("Welcomes")); 
  
        // Checking for the key_element 'World' 
        System.out.println("Is the key 'World' present? " +  
        li_hash_map.containsKey("World")); 
    } 
}

輸出：

Initial Mappings are: {Geeks=20, 4=15, Welcomes=25, You=30}
Is the key 'Welcomes' present? true
Is the key 'World' present? false

注意：可以使用具有不同數據類型的變化和組合的任何類型的映射來執行相同的操作。

相關用法

注：本文由純淨天空篩選整理自Chinmoy Lenka大神的英文原創作品 LinkedHashMap containsKey() Method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。