学步园

JDK1.5 才开始有枚举类型，同时可爱的 Java 组织丰富了 switch 语句：支持枚举。

定义一个枚举类 Color

public enum Color {
		RED("red color", 0), 
		GREEN("green color", 1),
		BLUE("blue color", 2), 
		YELLOW("yellow color", 3);

		Color(String name, int id) {
			_name = name;
			_id = id;
		}

		private String _name;
		private int _id;

		public String getName() {
			return _name;
		}

		public int getId() {
			return _id;
		}

		public static Color getColor(int max) {
			Random random = new Random(System.currentTimeMillis());
			int num = random.nextInt(max);
			switch (num) {
			case 0:
				return Color.RED;
			case 1:
				return Color.GREEN;
			case 2:
				return Color.BLUE;
			case 3:
				return Color.YELLOW;
			default:
				return Color.BLUE;
			}
		}
}

为 Color 提供了一个静态方法 getColor，可以随机获取颜色值。

那么，可以结合 switch 语句这样使用：

public static void main(String[] args) {
		int len = Color.values().length;
		Color color = Color.getColor(len);
		switch (color) {
		case RED:
			System.out.println("select " + "RED");
			break;
		case GREEN:
			System.out.println("select " + "GREEN");
			break;
		case BLUE:
			System.out.println("select " + "BLUE");
			break;
		case YELLOW:
			System.out.println("select " + "YELLOW");
			break;
		default:
			System.out.println("select " + "unknow!!");
			break;
		}
}

可以看出，switch 语句中是 Color 对象。

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完整代码

package mark.demo;

import java.util.Random;

public class EnumDemo {

	public static void main(String[] args) {
		int len = Color.values().length;
		Color color = Color.getColor(len);
		switch (color) {
		case RED:
			System.out.println("select " + "RED");
			break;
		case GREEN:
			System.out.println("select " + "GREEN");
			break;
		case BLUE:
			System.out.println("select " + "BLUE");
			break;
		case YELLOW:
			System.out.println("select " + "YELLOW");
			break;
		default:
			System.out.println("select " + "unknow!!");
			break;
		}
	}

	public enum Color {
		RED("red color", 0), 
		GREEN("green color", 1),
		BLUE("blue color", 2), 
		YELLOW("yellow color", 3);

		Color(String name, int id) {
			_name = name;
			_id = id;
		}

		private String _name;
		private int _id;

		public String getName() {
			return _name;
		}

		public int getId() {
			return _id;
		}

		public static Color getColor(int max) {
			Random random = new Random(System.currentTimeMillis());
			int num = random.nextInt(max);
			switch (num) {
			case 0:
				return Color.RED;
			case 1:
				return Color.GREEN;
			case 2:
				return Color.BLUE;
			case 3:
				return Color.YELLOW;
			default:
				return Color.BLUE;
			}
		}
	}
}