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  • 2018-09-03  08:30:05        
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    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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