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);
}
}