Java IdentityHashMap clear()用法及代码示例

Java中的java.util.IdentityHashMap.clear()方法用于清除和删除指定映射中的所有元素或映射。

用法:

Identity_HashMap.clear()

参数：该方法不接受任何参数。

返回值：该方法不返回任何值。

以下程序用于说明java.util.IdentityHashMap.clear()方法的用法：

示例1:将字符串值映射到整数键。

// Java code to illustrate the clear() method 
import java.util.*; 
  
public class Identity_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty IdentityHashMap 
        IdentityHashMap<Integer, String> identity_hash = new IdentityHashMap<Integer, String>(); 
  
        // Mapping string values to int keys 
        identity_hash.put(10, "Geeks"); 
        identity_hash.put(15, "4"); 
        identity_hash.put(20, "Geeks"); 
        identity_hash.put(25, "Welcomes"); 
        identity_hash.put(30, "You"); 
  
        // Displaying the IdentityHashMap 
        System.out.println("Initial Mappings are: "
                           + identity_hash); 
  
        // Clearing the map using clear() 
        identity_hash.clear(); 
  
        // Displaying the final IdentityHashMap 
        System.out.println("Final Map: "
                           + identity_hash); 
    } 
}

输出：

Initial Mappings are: {10=Geeks, 30=You, 20=Geeks, 25=Welcomes, 15=4}
Final Map: {}

示例2:将整数值映射到字符串键。

// Java code to illustrate the clear() method 
import java.util.*; 
  
public class Identity_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty IdentityHashMap 
        Map<String, Integer> identity_hash = new IdentityHashMap<String, Integer>(); 
  
        // Mapping int values to string keys 
        identity_hash.put("Geeks", 10); 
        identity_hash.put("4", 15); 
        identity_hash.put("Geeks", 20); 
        identity_hash.put("Welcomes", 25); 
        identity_hash.put("You", 30); 
  
        // Displaying the IdentityHashMap 
        System.out.println("Initial Mappings are: " + identity_hash); 
  
        // Clearing the map using clear() 
        identity_hash.clear(); 
  
        // Displaying the final IdentityHashMap 
        System.out.println("Final Map: "
                           + identity_hash); 
    } 
}

输出：

Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
Final Map: {}

注意：可以对具有不同数据类型的变体和组合的任何类型的映射执行相同的操作。

相关用法

注：本文由纯净天空筛选整理自Chinmoy Lenka大神的英文原创作品 IdentityHashMap clear() Method in Java。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。