Java EnumMap用法及代码示例

// Java Program to illustrate Working of EnumMap class 
// and its functions 
  
// Importing EnumMap class 
import java.util.EnumMap; 
  
// Main class 
public class EnumMapExample { 
  
    // Enum 
    public enum GFG { 
        CODE, 
        CONTRIBUTE, 
        QUIZ, 
        MCQ; 
    } 
  
    // Main driver method 
    public static void main(String args[]) 
    { 
  
        // Java EnumMap 
        // Creating an empty EnumMap with key 
        // as enum type state 
        EnumMap<GFG, String> gfgMap 
            = new EnumMap<GFG, String>(GFG.class); 
  
        // Putting values inside EnumMap in Java 
        // Inserting Enum keys different from 
        // their natural order 
        gfgMap.put(GFG.CODE, "Start Coding with gfg"); 
        gfgMap.put(GFG.CONTRIBUTE, "Contribute for others"); 
        gfgMap.put(GFG.QUIZ, "Practice Quizes"); 
        gfgMap.put(GFG.MCQ, "Test Speed with Mcqs"); 
  
        // Printing size of EnumMap 
        System.out.println("Size of EnumMap in java: "
                           + gfgMap.size()); 
  
        // Printing Java EnumMap 
        // Print EnumMap in natural order 
        // of enum keys (order on which they are declared) 
        System.out.println("EnumMap: " + gfgMap); 
  
        // Retrieving value from EnumMap 
        System.out.println("Key : " + GFG.CODE + " Value: "
                           + gfgMap.get(GFG.CODE)); 
  
        // Checking if EnumMap contains a particular key 
        System.out.println( 
            "Does gfgMap has " + GFG.CONTRIBUTE + ": "
            + gfgMap.containsKey(GFG.CONTRIBUTE)); 
  
        // Checking if EnumMap contains a particular value 
        System.out.println( 
            "Does gfgMap has :" + GFG.QUIZ + " : "
            + gfgMap.containsValue("Practice Quizes")); 
        System.out.println("Does gfgMap has :" + GFG.QUIZ 
                           + " : "
                           + gfgMap.containsValue(null)); 
    } 
}

// Java Program to Add Elements to the EnumMap 
  
// Importing EnumMap class 
import java.util.EnumMap; 
  
// Main class 
// AddingElementsToEnumMap 
class GFG { 
  
    enum Color { RED, GREEN, BLUE, WHITE } 
    public static void main(String[] args) 
    { 
  
        // Creating an EnumMap of the Color enum 
        EnumMap<Color, Integer> colors1 
            = new EnumMap<>(Color.class); 
  
        // Insert elements in Map 
        // using put() method 
        colors1.put(Color.RED, 1); 
        colors1.put(Color.GREEN, 2); 
  
        // Printing mappings to the console 
        System.out.println("EnumMap colors1: " + colors1); 
  
        // Creating an EnumMap of the Color Enum 
        EnumMap<Color, Integer> colors2 
            = new EnumMap<>(Color.class); 
  
        // Adding elements using the putAll() method 
        colors2.putAll(colors1); 
        colors2.put(Color.BLUE, 3); 
  
        // Printing mappings to the console 
        System.out.println("EnumMap colors2: " + colors2); 
    } 
}

// Java Program to Access the Elements of EnumMap 
  
// Importing required classes 
import java.util.EnumMap; 
  
// Main class 
// AccessElementsOfEnumMap 
class GFG { 
  
    // Enum 
    enum Color { RED, GREEN, BLUE, WHITE } 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
  
        // Creating an EnumMap of the Color enum 
        EnumMap<Color, Integer> colors 
            = new EnumMap<>(Color.class); 
  
        // Inserting elements using put() method 
        colors.put(Color.RED, 1); 
        colors.put(Color.GREEN, 2); 
        colors.put(Color.BLUE, 3); 
        colors.put(Color.WHITE, 4); 
  
        System.out.println("EnumMap colors : " + colors); 
  
        // Using the entrySet() method 
        System.out.println("Key/Value mappings: "
                           + colors.entrySet()); 
  
        // Using the keySet() method 
        System.out.println("Keys: " + colors.keySet()); 
  
        // Using the values() method 
        System.out.println("Values: " + colors.values()); 
  
        // Using the get() method 
        System.out.println("Value of RED : "
                           + colors.get(Color.RED)); 
    } 
}

// Java program to Remove Elements of EnumMap 
  
// Importing EnumMap class 
import java.util.EnumMap; 
  
// Main class 
class GFG { 
  
    // Enum 
    enum Color { 
  
        // Custom elements 
        RED, 
        GREEN, 
        BLUE, 
        WHITE 
    } 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
  
        // Creating an EnumMap of the Color enum 
        EnumMap<Color, Integer> colors 
            = new EnumMap<>(Color.class); 
  
        // Inserting elements in the Map 
        // using put() method 
        colors.put(Color.RED, 1); 
        colors.put(Color.GREEN, 2); 
        colors.put(Color.BLUE, 3); 
        colors.put(Color.WHITE, 4); 
  
        // Printing colors in the EnumMap 
        System.out.println("EnumMap colors : " + colors); 
  
        // Removing a mapping 
        // using remove() Method 
        int value = colors.remove(Color.WHITE); 
  
        // Displaying the removed value 
        System.out.println("Removed Value: " + value); 
  
        // Removing specific color and storing boolean 
        // if removed or not 
        boolean result = colors.remove(Color.RED, 1); 
  
        // Printing the boolean result whether removed or 
        // not 
        System.out.println("Is the entry {RED=1} removed? "
                           + result); 
  
        // Printing the updated Map to the console 
        System.out.println("Updated EnumMap: " + colors); 
    } 
}

// Java Program to Replace Elements of EnumMap 
  
// Importing required classes 
import java.util.EnumMap; 
  
// Main class 
class GFG { 
  
    // Enum 
    enum Color { 
  
        RED, 
        GREEN, 
        BLUE, 
        WHITE 
    } 
  
    // Main driver method 
    public static void main(String[] args) 
    { 
  
        // Creating an EnumMap of the Color enum 
        EnumMap<Color, Integer> colors 
            = new EnumMap<>(Color.class); 
  
        // Inserting elements to Map 
        // using put() method 
        colors.put(Color.RED, 1); 
        colors.put(Color.GREEN, 2); 
        colors.put(Color.BLUE, 3); 
        colors.put(Color.WHITE, 4); 
  
        // Printing all elements inside above Map 
        System.out.println("EnumMap colors " + colors); 
  
        // Replacing certain elements depicting colors 
        // using the replace() method 
        colors.replace(Color.RED, 11); 
        colors.replace(Color.GREEN, 2, 12); 
  
        // Printing the updated elements (colors) 
        System.out.println("EnumMap using replace(): "
                           + colors); 
  
        // Replacing all colors using the replaceAll() 
        // method 
        colors.replaceAll((key, oldValue) -> oldValue + 3); 
  
        // Printing the elements of above Map 
        System.out.println("EnumMap using replaceAll(): "
                           + colors); 
    } 
}

import java.util.EnumMap; 
import java.util.Map; 
  
public class EnumMapExample { 
      
    enum Color { 
        RED, GREEN, BLUE 
    } 
      
    public static void main(String[] args) { 
        // create an EnumMap with Color enum as keys and String as values 
        EnumMap<Color, String> colorMap = new EnumMap<>(Color.class); 
          
        // add some key-value pairs to the map 
        colorMap.put(Color.RED, "FF0000"); 
        colorMap.put(Color.GREEN, "00FF00"); 
        colorMap.put(Color.BLUE, "0000FF"); 
          
        // print the map 
        System.out.println("Color map: " + colorMap); 
          
        // get the value associated with a particular key 
        String greenValue = colorMap.get(Color.GREEN); 
        System.out.println("Value for GREEN: " + greenValue); 
          
        // iterate over the map and print all key-value pairs 
        System.out.println("All key-value pairs:"); 
        for (Map.Entry<Color, String> entry : colorMap.entrySet()) { 
            System.out.println(entry.getKey() + " -> " + entry.getValue()); 
        } 
    } 
}