자바 enum 정리

사용법 1  :   클래스의 멤버로 사용 

public enum Currency {PENNY, NICKLE, DIME, QUARTER};

Currency coin = Currency.PENNY;

coin = 1; //compilation error

사용법 2  :   클래스의 멤버로 사용 (값을 지정) 

public enum Currency {PENNY(1), NICKLE(5), DIME(10), QUARTER(25)};

사용법 3  :   Switch 문의 인자로 사용  

Currency usCoin = Currency.DIME;

    switch (usCoin) {

            case PENNY:

                    System.out.println("Penny coin");

                    break;

            case NICKLE:

                    System.out.println("Nickle coin");

                    break;

            case DIME:

                    System.out.println("Dime coin");

                    break;

            case QUARTER:

                    System.out.println("Quarter coin");

    }

사용법 4  :   enum 안에 정의된 상수들은 final 이라, == 으로 비교가능 

Currency usCoin = Currency.DIME;

    if(usCoin == Currency.DIME){

       System.out.println("enum in java can be"+

               "compared using ==");

    }

사용법 5  :   enum 안에 정의된 상수들은 final 이라, == 으로 비교가능 

사용법 6  :  메소드 확장하기 

public enum SizeEnum {

  SMALL("S"), MEDIUM("M"), LARGE("L");

  // Fields

  private String mAbbreviation;

  // Constructor

  private SizeEnum(String abbreviation) {

   mAbbreviation = abbreviation;

  }

   

  // Methods

  public String getAbbreviation() { return mAbbreviation; }

  public void setAbbreviation(String abbreviation) { mAbbreviation = abbreviation; }

 

}

사용법 7  :  Enum 클래스로 사용하기 

public enum FontStyle {

    NORMAL, BOLD, ITALIC, UNDERLINE;

 

    FontStyle() {

    }

}




인라인 클래스로 사용  ( sample.FontStyle.NORMAL  접근) 

public enum SampleClass {

    public enum FontStyle { NORMAL, BOLD, ITALIC, UNDERLINE }

    ...

}

사용법 7  :  EnumSet 사용하기
import java.util.EnumSet;

import java.util.Set;

/**
 * Simple Java Program to demonstrate how to use EnumSet.
 * It has some interesting use cases and it's specialized collection for
 * Enumeration types. Using Enum with EnumSet will give you far better
 * performance than using Enum with HashSet, or LinkedHashSet.
 *
 * @author Javin Paul
 */
public class EnumSetDemo {

    private enum Color {
        RED(255, 0, 0), GREEN(0, 255, 0), BLUE(0, 0, 255);
        private int r;
        private int g;
        private int b;
        private Color(int r, int g, int b) {
            this.r = r;
            this.g = g;
            this.b = b;
        }
        public int getR() {
            return r;
        }
        public int getG() {
            return g;
        }
        public int getB() {
            return b;
        }
    }


    public static void main(String args[]) {
        // this will draw line in yellow color
        EnumSet<Color> yellow = EnumSet.of(Color.RED, Color.GREEN);
        drawLine(yellow);
        // RED + GREEN + BLUE = WHITE
        EnumSet<Color> white = EnumSet.of(Color.RED, Color.GREEN, Color.BLUE);
        drawLine(white);
        // RED + BLUE = PINK
        EnumSet<Color> pink = EnumSet.of(Color.RED, Color.BLUE);
        drawLine(pink);
    }


    public static void drawLine(Set<Color> colors) {
        System.out.println("Requested Colors to draw lines : " + colors);
        for (Color c : colors) {
            System.out.println("drawing line in color : " + c);
        }
    }
}

Output:
Requested Colors to draw lines : [RED, GREEN]
drawing line in color : RED
drawing line in color : GREEN

Requested Colors to draw lines : [RED, GREEN, BLUE]
drawing line in color : RED
drawing line in color : GREEN
drawing line in color : BLUE

Requested Colors to draw lines : [RED, BLUE]
drawing line in color : RED
drawing line in color : BLUE

사용법 8  :  EnumSet 으로 비트필드 대체하기 

package resolver;

public class IntEnumPatternExample {

    public static final int STYLE_BOLD          = 1 << 0; // 1
    public static final int STYLE_ITALIC        = 1 << 1; // 2
    public static final int STYLE_UNDERLINE     = 1 << 2; // 4
    public static final int STYLE_STRIKETHROUGH = 1 << 3; // 8

    public static void main(String[] args) {
        final IntEnumPatternResolver resolver = new IntEnumPatternResolver();
        resolver.enableAll(STYLE_BOLD, STYLE_ITALIC, STYLE_STRIKETHROUGH, STYLE_UNDERLINE);
        resolver.disable(STYLE_STRIKETHROUGH);
        resolver.toggle(STYLE_UNDERLINE);
        print(resolver);
    }

    private static void print(IntEnumPatternResolver resolver) {
        assert resolver.isEnabled(STYLE_BOLD) == true;
        assert resolver.isEnabled(STYLE_ITALIC) == true;
        assert resolver.isEnabled(STYLE_UNDERLINE) == false;
        assert resolver.isEnabled(STYLE_STRIKETHROUGH) == false;

        System.out.println("STYLE_BOLD: " + resolver.isEnabled(STYLE_BOLD));
        System.out.println("STYLE_ITALIC: " + resolver.isEnabled(STYLE_ITALIC));
        System.out.println("STYLE_UNDERLINE: " + resolver.isEnabled(STYLE_UNDERLINE));
        System.out.println("STYLE_STRIKETHROUGH: " + resolver.isEnabled(STYLE_STRIKETHROUGH));
    }

}

package resolver;

import java.util.EnumSet;

public class EnumPatternExample {

    public enum Style {
        BOLD, ITALIC, UNDERLINE, STRIKETHROUGH
    }

    public static void main(String[] args) {
        final EnumSet<Style> styles = EnumSet.noneOf(Style.class);
        styles.addAll(EnumSet.range(Style.BOLD, Style.STRIKETHROUGH)); // enable all constants
        styles.removeAll(EnumSet.of(Style.UNDERLINE, Style.STRIKETHROUGH)); // disable a couple
        assert EnumSet.of(Style.BOLD, Style.ITALIC).equals(styles); // check set contents are correct
        System.out.println(styles);
    }

}

http://claude-martin.ch/enumbitset/  완전한 EnumBitSet 라이브러리 

사용법 8  :  EnumMap 사용하기 

enum Importance {
Low, Medium, High, Critical
}

EnumMap<Importance, String> enumMap = new EnumMap<>(Importance.class);

enumMap.put(Importance.Low, "=Low");
enumMap.put(Importance.High, "=High");

String value1 = enumMap.get(Importance.Low);
String value2 = enumMap.get(Importance.High);

package program;
import java.util.EnumMap;
public class Program {
    // 1. Create an Enum.
    enum Importance {
Low, Medium, High, Critical
    }
    public static void main(String[] args) {
        // 2. Create an EnumMap.
        EnumMap<Importance, String> enumMap = new EnumMap<>(Importance.class);
        // 3. PUT values into the map.
        enumMap.put(Importance.Low, "=Low");
        enumMap.put(Importance.High, "=High");
        // 4. Get values from the map.
        String value1 = enumMap.get(Importance.Low);
        String value2 = enumMap.get(Importance.High);
        System.out.println(value1);
        System.out.println(value2);
    }
}