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Java LinkedHashMap containsKey()用法及代码示例


java.util.LinkedHashMap.containsKey() 方法用于检查特定键是否映射到LinkedHashMap 中。它将关键元素作为参数,如果该元素已映射到映射中,则返回 True。
用法:

Linked_Hash_Map.containsKey(key_element)

参数:该方法只需要一个参数key_element它指的是应该在映射内检查其映射的键。

返回类型:如果检测到 key 存在,该方法返回布尔值 true,否则返回 false。

示例 1:将字符串值映射到整数键。

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)); 
    } 
} 
输出:
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:将整数值映射到字符串键。

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")); 
    } 
} 
输出:
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:可以使用具有不同数据类型的变化和组合的任何类型的映射来执行相同的操作。



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注:本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 LinkedHashMap containsKey() Method in Java with Examples。非经特殊声明,原始代码版权归原作者所有,本译文未经允许或授权,请勿转载或复制。