Java 枚舉：switch 支持枚舉

JDK1.5 才開始有枚舉類型，同時可愛的 Java 組織豐富了 switch 語句：支持枚舉。

定義一個枚舉類 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;
			}
		}
}

為 Color 提供了一個靜態方法 getColor，可以隨機獲取顏色值。

那么，可以結合 switch 語句這樣使用：

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 語句中是 Color 對象。

------------------------------附錄

完整代碼

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;
			}
		}
	}
}

轉自：https://blog.csdn.net/veryitman/article/details/7947640