Java中, IdentityHashMap size() 的方法

作者: Arvin Chen 分类: Java 来源: Break易站(www.breakyizhan.com)

IdentityHashMap类的java.util.IdentityHashMap.size()方法用于获取IdentityHashMap的大小,该大小是指Map中键值对或映射的数量。

句法:

Identity_Hash_Map.size()

参数:该方法不接受任何参数。

返回值:该方法返回映射的大小,这也表示映射中存在的键值对的数量。

下面的程序说明了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

程序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
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