Java WeakHashMap remove()用法及代碼示例

java.util.WeakHashMap.remove()是WeakHashMap類的內置方法，用於從映射中刪除任何特定鍵的映射。它本質上刪除了Map中任何特定鍵的值。

用法:

Weak_Hash_Map.remove(Object key)

參數：該方法采用一個參數鍵，該鍵的映射關係將從Map中刪除。

返回值：如果該鍵存在，則該方法返回先前映射到指定鍵的值，否則該方法返回NULL。

以下示例程序旨在說明java.util.WeakHashMap.remove()方法的用法：
示例1:傳遞現有 key 時。

// Java code to illustrate the remove() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<Integer, String> weak_hash = new 
                       WeakHashMap<Integer, String>(); 
    
        // Mapping string values to int keys 
        weak_hash.put(10, "Geeks"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Geeks"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " +  
                                           weak_hash); 
  
        // Removing the existing key mapping 
        String returned_value =  
                         (String)weak_hash.remove(20); 
  
        // Verifying the returned value 
        System.out.println("Returned value is: " +  
                                      returned_value); 
  
        // Displayin the new map 
        System.out.println("New map is: " + weak_hash); 
    } 
}

輸出：

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: Geeks
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes}

示例2:傳遞新 key 時。

// Java code to illustrate the remove() method 
import java.util.*; 
  
public class Weak_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty WeakHashMap 
        Map<Integer, String> weak_hash =  
                   new WeakHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        weak_hash.put(10, "Geeks"); 
        weak_hash.put(15, "4"); 
        weak_hash.put(20, "Geeks"); 
        weak_hash.put(25, "Welcomes"); 
        weak_hash.put(30, "You"); 
  
        // Displaying the WeakHashMap 
        System.out.println("Initial Mappings are: " +  
                                          weak_hash); 
  
        // Removing the new key mapping 
        String returned_value =  
                        (String)weak_hash.remove(50); 
  
        // Verifying the returned value 
        System.out.println("Returned value is: " +  
                                    returned_value); 
  
        // Displayin the new map 
        System.out.println("New map is: "+weak_hash); 
    } 
}

輸出：

Initial Mappings are: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}
Returned value is: null
New map is: {30=You, 15=4, 10=Geeks, 25=Welcomes, 20=Geeks}

注意：可以對具有不同數據類型的變化和組合的任何類型的映射執行相同的操作。

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 WeakHashMap remove() method in Java。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。