Java IdentityHashMap size()用法及代碼示例

IdentityHashMap類的java.util.IdentityHashMap.size()方法用於獲取IdentityHashMap的大小，該IdentityHashMap引用Map中的鍵值對或映射的數量。

用法:

Identity_Hash_Map.size()

參數：該方法不帶任何參數。

返回值：該方法返回Map的大小，這也意味著Map中存在的鍵值對的數量。

以下示例程序旨在說明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()); 
    } 
}

輸出：

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()); 
    } 
}

輸出：

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

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 IdentityHashMap size() 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。