Java IdentityHashMap size()用法及代码示例

IdentityHashMap类的java.util.IdentityHashMap.size()方法用于获取IdentityHashMap的大小，该IdentityHashMap引用Map中的键值对或映射的数量。

用法:

Identity_Hash_Map.size()

参数：该方法不带任何参数。

返回值：该方法返回Map的大小，这也意味着Map中存在的键值对的数量。

以下示例程序旨在说明java.util.IdentityHashMap.size()方法：

程序1：

// Java code to illustrate the size() method 
import java.util.*; 
  
public class Identity_Hash_Map_Demo { 
    public static void main(String[] args) 
    { 
  
        // Creating an empty IdentityHashMap 
        Map<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); 
  
        // Displaying the size of the map 
        System.out.println("The size of the map is " +  
                                    identity_hash.size()); 
    } 
}

输出：

Initial Mappings are: {Geeks=20, Welcomes=25, You=30, 4=15}
The size of the map is 4

示例2:

// Java code to illustrate the size() 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); 
  
        // Displaying the size of the map 
        System.out.println("The size of the map is " +  
                                     identity_hash.size()); 
    } 
}

输出：

Initial Mappings are: {Welcomes=25, 4=15, You=30, Geeks=20}
The size of the map is 4

注意：可以对具有不同数据类型的变化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 size() 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。