Java中EnumMap的size()方法: Java.util.EnumMap.size()

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

Java中的Java.util.EnumMap.size()方法用于了解map的大小或map中存在的元素数量。

句法:

Enum_Map.size()

参数:该方法不接受任何参数。

返回值:该方法返回map的大小。

下面的程序说明了size()函数的工作原理

程序1:

// Java program to demonstrate size()
import java.util.*;

// An enum of geeksforgeeks
public enum gfg {
    India_today,
    United_States_today
}
;

class Enum_demo {
    public static void main(String[] args)
    {

        EnumMap<gfg, Integer> mp = new
                    EnumMap<gfg, Integer>(gfg.class);

        // Values are associated
        mp.put(gfg.India_today, 69);
        mp.put(gfg.United_States_today, 1073);

        // Prints the map
        System.out.println("The EnumMap: " + mp);

        // Store the size of the map
        int numberOf_kv = mp.size();

        // Prints the map_size
        System.out.println("Size of map: " + numberOf_kv);
    }
}

输出:

The EnumMap: {India_today=69, United_States_today=1073}
Size of map: 2

程序2:

// Java program to demonstrate size()
import java.util.*;

// An enum of geeksforgeeks
public enum gfg {

    India_today,
    United_States_today
}
;

class Enum_demo {
    public static void main(String[] args)
    {

        EnumMap<gfg, Integer> mp = new
                  EnumMap<gfg, Integer>(gfg.class);

        // Values are associated
        mp.put(gfg.India_today, 69);
        mp.put(gfg.United_States_today, 1073);

        // Prints the map
        System.out.println("The EnumMap: " + mp);

        // Remove mapping of this key
        mp.remove(gfg.United_States_today);

        // Prints the final map
        System.out.println("The EnumMap: " + mp);

        // Store the size pf map after removal of
        // The key
        int numberOf_kv = mp.size();

        // Prints the map_size
        System.out.println("Size of map: " + numberOf_kv);
    }
}

输出:

The EnumMap: {India_today=69, United_States_today=1073}
The EnumMap: {India_today=69}
Size of map: 1
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