Enum的例子

Enum 可以用于存储常量列表，也可以作单例SingleTon，其中，单例应用更是所有单例实现中的最佳实践。以下是一个例子：

public class Enum01 {

	public static void main(String[] args) {
		basicTest();
//		singleTon();
	}
	
	public static void basicTest() {
		Token token = Token.NAME;
		// enum's method
		System.out.println("~~~basicTest~~~");
		System.out.println(token.name());
		// 只是用作常量的话，用name()就好
		System.out.println(Token.NAME.name());
		System.out.println(Token.NAME.compareTo(Token.NAME1));
		System.out.println(Token.values()[0].name);
		System.out.println(Token.valueOf("NAME1").name);
		// enum in switch
		switch (token) {
		case NAME:
			System.out.println("NAME");
			break;
		case NAME1:
			System.out.println("NAME1");
			break;
		default:
			System.out.println("default");
			break;
		}
		System.out.println("~~~basicTest end~~~");
	}
	
	public static void singleTon() {
		// same instance 
		Token token = Token.COUNTER;
		Token token1 = Token.COUNTER;
		if (token == token1) {
			System.out.println("same object");
		}
		token.addCounter(1);
		token1.addCounter(1);
		System.out.println(token1.counter);
	}

	// 枚举类
	private enum Token {
		// 本质是类静态常量(public static final), 所以大写
		NAME, NAME1("name1"), COUNTER(1);
		
		private String name;
		private int counter = 0;
		// constructor(private, initialize once)
		private Token() {
			this.name = "init_name";
			System.out.println("Singleton instance created.");
		}
		private Token(String name) {
			this.name = name;
			System.out.println("Singleton2 instance created.");
		}
		private Token(int counter) {
			this.counter += counter;
			System.out.println(this.counter);
		}
		// singleton一般有对应的方法而不只是定义常量
		private void addCounter(int counter) {
			this.counter += counter;
			System.out.println(this.counter);
		}
	}
}