Enumerations

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Enums1.java

import java.util.HashMap;
import java.util.Map;
import org.pureprogrammer.Utils;

public class Enums1 {

	enum CompassPoint {
		NORTH, EAST, SOUTH, WEST
	}

	static String CompassPointToString(final CompassPoint c) {
		String result = "";
		switch (c) {
			case NORTH:
				result = "North";
				break;
			case EAST:
				result = "East";
				break;
			case SOUTH:
				result = "South";
				break;
			case WEST:
				result = "West";
				break;
		}
		return result;
	}

	static CompassPoint turnRight(final CompassPoint c) {
		if (c == CompassPoint.NORTH) {
			return CompassPoint.EAST;
		} else if (c == CompassPoint.EAST) {
			return CompassPoint.SOUTH;
		} else if (c == CompassPoint.SOUTH) {
			return CompassPoint.WEST;
		} else {
			return CompassPoint.NORTH;
		}
	}

	public static void main(String[] args) {
		CompassPoint cp1 = CompassPoint.NORTH;
		System.out.println("cp1: " + cp1);
		System.out.println("SOUTH: " + CompassPointToString(CompassPoint.SOUTH));
		System.out.println("turnRight(cp1): " + CompassPointToString(turnRight(cp1)));
		CompassPoint cp2 = CompassPoint.EAST;
		if (cp1 == cp2) {
			System.out.println("cp1 == cp2");
		} else {
			System.out.println("cp1 != cp2");
		}
		cp1 = cp2;
		if (cp1 == cp2) {
			System.out.println("cp1 == cp2");
		} else {
			System.out.println("cp1 != cp2");
		}
	}
}

Enums2.java

import java.util.HashMap;
import java.util.Map;
import org.pureprogrammer.Utils;

public class Enums2 {

	enum Color {
		RED(1),
		GREEN(2),
		YELLOW(3),
		BLUE(4),
		MAGENTA(5),
		CYAN(6);

		private static Map<Integer, Color> byValue = new HashMap<>();
		static {
		    for (Color e: values()) {
		        byValue.put(e.value, e);
		    }
		}
		public final int value;
		private Color(int v) { value = v; }
		public int value() { return value; }
		public static Color valueOf(int i) {
		    Color result = byValue.get(i);
		    return result;
		}
	}

	static Color combineColors(final Color c1, final Color c2) {
		final int i1 = c1.value();
		final int i2 = c2.value();
		final int result = i1 | i2;
		final Color returnColor = Color.valueOf(result);
		return returnColor;
	}

	public static void main(String[] args) {
		Color c1 = Color.BLUE;
		System.out.println("c1: " + c1);
		System.out.println("RED: " + Color.RED);
		System.out.println("combineColors(c1, RED): " + combineColors(c1, Color.RED));
		Color c2 = Color.GREEN;
		System.out.println("combineColors(c1, c2): " + combineColors(c1, c2));
		if (c1 == c2) {
			System.out.println("c1 == c2");
		} else {
			System.out.println("c1 != c2");
		}
		c1 = c2;
		if (c1 == c2) {
			System.out.println("c1 == c2");
		} else {
			System.out.println("c1 != c2");
		}
		Color bad = Color.valueOf(7);
		System.out.println("bad: " + bad);
	}
}

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References

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