定义一个交通灯枚举

定义一个交通灯枚举，包含红灯、绿灯、黄灯，需要有获得下一个灯的方法，例如：红灯获取下一个灯是绿灯，绿灯获取下一个灯是黄灯。

package com.alex.question1;

public enum TrafficLight {
	RED,GREEN,YELLOW;
	
	public static TrafficLight getNextLight(TrafficLight currentLight){
		switch(currentLight){
		case RED:
			return GREEN;
		case GREEN:
			return YELLOW;
		case YELLOW:
			return RED;
		}
		return null;
	}
}

package com.alex.question1;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

public class TrafficLightTest{
	@Test
	public void test1(){
		assertEquals(TrafficLight.GREEN,TrafficLight.getNextLight(TrafficLight.RED));
		assertEquals(TrafficLight.YELLOW,TrafficLight.getNextLight(TrafficLight.GREEN));
		assertEquals(TrafficLight.RED,TrafficLight.getNextLight(TrafficLight.YELLOW));
	}
}