switch中使用枚举 提高可读性（1.6之前switch不支持String）

[java]代码库

enum Signal {
    GREEN, YELLOW, RED
}
public class TrafficLight {
    Signal color = Signal.RED;
    public void change() {
        switch (color) {
        case RED:
            color = Signal.GREEN;
            break;
        case YELLOW:
            color = Signal.RED;
            break;
        case GREEN:
            color = Signal.YELLOW;
            break;
        }
    }
}