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  • 2018-08-31  23:16:23        
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    Java中的Java.util.EnumMap.put(key,value)方法用于关联指定的键值对。在这种情况下,如果重复这些值,则替换旧值。

    句法:

    Enum_Map.put(key, value)

    使用的参数:该方法有两个参数。

    • key - 与值关联的指定键。
    • value - 它是与指定键关联的值。

    返回值:该函数返回与指定键关联的旧值。

    下面的程序说明了put(key,value)方法的工作原理

    Java.util.EnumMap.put(key,value)程序1:

    // Java program to demonstrate keySet()
    import java.util.*;
    
    // An enum of geeksforgeeks
    public enum gfg {
        Global_today,
        India_today,
        China
    }
    ;
    
    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.Global_today, 799);
            mp.put(gfg.India_today, 69);
    
           // Display the initial map
           System.out.println("The map is: " + mp);
    
            // Stores the old value associated with the key
            int prev_value = mp.put(gfg.India_today, 72);
    
            // Prints the old value
            System.out.println("Previous value: " + prev_value);
    
           // Display the final map
           System.out.println("The final map is: " + mp);
        }
    }
    

    输出:

    The map is: {Global_today=799, India_today=69}
    Previous value: 69
    The final map is: {Global_today=799, India_today=72}

    Java.util.EnumMap.put(key,value)程序2:

    // Java program to demonstrate the working of keySet()
    import java.util.*;
    
    // an enum of geeksforgeeks
    // ranking globally and in india
    public enum gfg {
        Global_today,
        India_today,
        China_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.Global_today, 799);
            mp.put(gfg.India_today, 69);
    
           // Display the initial map
           System.out.println("The map is: " + mp);
    
            // Stores the old value associated with the key
            int prev_value = mp.put(gfg.Global_today, 800);
    
            // Prints the old value
            System.out.println("Previous value: " + prev_value);
    
           // Display the final map
           System.out.println("The final map is: " + mp);
        }
    }
    

    输出:

    The map is: {Global_today=799, India_today=69}
    Previous value: 799
    The final map is: {Global_today=800, India_today=69}

     
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