public class Road {
 private List<String> vechicles = new ArrayList<String>();

 private String name;

 public Road(String name) {
  this.name = name;

  // 開啟一個線程： 模擬車輛不斷隨機上路的過程, 1-10s會產(chǎn)生一輛車  
  ExecutorService pool = Executors.newSingleThreadExecutor();
  pool.execute(new Runnable() {
   public void run() {
    for (int i = 1; i < 1000; i++) {
     try {
      Thread.sleep((new Random().nextInt(10) + 1) * 1000);
      vechicles.add(Road.this.name + "_" + i);
     } catch (InterruptedException e) {
      e.printStackTrace();
     }
    }
   }
  });

  // 開啟定時器：每隔一秒檢查相應(yīng)的燈是否為綠，是則放行一輛車  
  ScheduledExecutorService timer = Executors.newScheduledThreadPool(1);
  timer.scheduleAtFixedRate(new Runnable() {
   public void run() {
    if (vechicles.size() > 0) {
     boolean lighted = Lamp.valueOf(Road.this.name).isLighted();
     if (lighted) {
      System.out.println(vechicles.remove(0) + " is traversing !");
     }
    }
   }
  }, 1, 1, TimeUnit.SECONDS);
 }
}

/**
 * 每一個Lamp元素代表一個方向上的燈，總共同擁有12個方向。全部總共同擁有12個Lamp元素。
 * 有例如以下方向上的燈,每兩個形成一組，一組燈同一時候變綠或變紅，所以，程序代碼僅僅須要控制每組燈中的一個燈就可以：
 * s2n,n2s    
 * s2w,n2e
 * e2w,w2e
 * e2s,w2n
 * -------
 * s2e,n2w
 * e2n,w2s
 * 上面最后兩行的燈是虛擬的。因為從南向東和從西向北、以及它們的相應(yīng)方向不受紅綠燈的控制。所以，能夠假想它們總是綠燈。

 */
public enum Lamp {
 // 每一個枚舉元素各表示一個方向的控制燈
 S2N("N2S", "S2W", false), S2W("N2E", "E2W", false), E2W("W2E", "E2S", false), E2S("W2N", "S2N", false),
 // 以下元素表示與上面的元素的相反方向的燈，它們的“相反方向燈”和“下一個燈”應(yīng)忽略不計！
 N2S(null, null, false), N2E(null, null, false), W2E(null, null, false), W2N(null, null, false),
 // 由南向東和由西向北等右拐彎的燈不受紅綠燈的控制，所以，能夠假想它們總是綠燈
 S2E(null, null, true), E2N(null, null, true), N2W(null, null, true), W2S(null, null, true);

 private Lamp(String opposite, String next, boolean lighted) {
  this.opposite = opposite;
  this.next = next;
  this.lighted = lighted;
 }

 // 當前燈是否為綠
 private boolean lighted;

 // 與當前燈同一時候為綠的相應(yīng)方向
 private String opposite;

 // 當前燈變紅時下一個變綠的燈
 private String next;

 public boolean isLighted() {
  return lighted;
 }

 /**
  * 某個燈變綠時。它相應(yīng)方向的燈也要變綠
  */
 public void light() {
  this.lighted = true;
  if (opposite != null) {
   Lamp.valueOf(opposite).light();
  }
  System.out.println(name() + " lamp is green。以下總共應(yīng)該有6個方向能看到汽車穿過！");
 }

 /**
  * 某個燈變紅時，相應(yīng)方向的燈也要變紅，而且下一個方向的燈要變綠
  * @return 下一個要變綠的燈
  */
 public Lamp blackOut() {
  this.lighted = false;
  if (opposite != null) {
   Lamp.valueOf(opposite).blackOut();
  }

  Lamp nextLamp = null;
  if (next != null) {
   nextLamp = Lamp.valueOf(next);
   System.out.println("綠燈從" + name() + "-------->切換為" + next);
   nextLamp.light();
  }
  return nextLamp;
 }
}

public class LampController {
 private Lamp currentLamp;

 public LampController() {
  // 剛開始讓由南向北的燈變綠;  
  currentLamp = Lamp.S2N;
  currentLamp.light();

  // 開啟定時器：每隔10秒將當前綠燈變?yōu)榧t燈，并讓下一個方向的燈變綠
  ScheduledExecutorService timer = Executors.newScheduledThreadPool(1);
  timer.scheduleAtFixedRate(new Runnable() {
   public void run() {
    currentLamp = currentLamp.blackOut();
   }
  }, 10, 10, TimeUnit.SECONDS);
 }
}

public class MainClass {

 public static void main(String[] args) {
  // 產(chǎn)生12個方向的路線 
  String[] directions = new String[] { 
    "S2N", "S2W", "E2W", "E2S", "N2S", "N2E", 
    "W2E", "W2N", "S2E", "E2N", "N2W", "W2S" 
  };
  
  for (int i = 0; i < directions.length; i++) {
   new Road(directions[i]);
  }

  // 產(chǎn)生整個交通燈系統(tǒng)
  new LampController();
 }
}