黑马程序员-7K月薪面试题破解之一_交通灯管理系统

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项目需求：模拟实现十字路口的交通灯管理系统逻辑，具体需求如下

异步随机生成按照各个路线行驶的车辆。

例如：由南向而来去往北向的车辆------直行车辆

由西向而来去往南向的车辆------右转车辆

由东向而来去往南向的车辆------左转车辆

如图：



信号灯忽略黄灯，只考虑红灯和绿灯。

应考虑左转车辆控制信号灯，右转车辆不受信号灯控制。

注：南北向车辆与东西向车辆交替放行，同方向等待车辆应先放行直行车辆而后放行左转车辆。每辆车通过路口时间为1秒（提示：可通过现场Sleep的方式模拟）。随机生成车辆时间间隔以及红绿灯交换时间间隔自定，可以设置。不要求实效GUI，只考虑系统逻辑实现，可通过Log方式展现程序运行结果。

Road类的编写：

package org.it315.interview.traffic;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
/*车开开到路上的代码  */

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

private String name = null;  //定义路线的名字
public Road(String name){
this.name = name;
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);
}catch(InterruptedException e){
e.printStackTrace();
}
vechicles.add(Road.this.name + " " + i);
}
}
});

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);

}

}

Lamp类的编写：

package org.it315.interview.traffic;

public enum Lamp {
S2N("N2S", "S2W",false),S2W("N2E","E2W",false),E2W("W2E","E2S",false),E2S("W2N","S2N",false),
N2S(null,null,false),N2E(null,null,false),W2E(null,null,false),W2N(null,null,false)  ,
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;
}

private Lamp(){

}

private boolean lighted;
private String opposite;
private String next;

public boolean isLighted(){
return lighted;
}

public void light(){
this.lighted = true;
if(opposite != null){
Lamp.valueOf(opposite).light();//返回该名字的枚举对象。
}
System.out.println(name()+" lamp is green,下面总共应该有6个方向能看到汽车穿过！");
}
public Lamp blackOut(){
this.lighted = false;
if(opposite != null){
Lamp.valueOf(opposite).blackOut();
}
Lamp nextLamp = null;
if(next != null){
nextLamp = Lamp.valueOf(next);
nextLamp.light();
System.out.println("绿灯"+ name() + "----------->切换为"+next );
}
return nextLamp;
}

}

LampController类的编写：

package org.it315.interview.traffic;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class LampController {
private Lamp currentLamp;
public LampController(){
currentLamp= Lamp.S2N;
currentLamp.light();

ScheduledExecutorService timer = Executors.newScheduledThreadPool(1);
timer.scheduleAtFixedRate(
new Runnable(){
public void run(){
currentLamp=currentLamp.blackOut();
}
},
10,
10,
TimeUnit.SECONDS);

}
}

Main类的编写：

package org.it315.interview.traffic;

public class MainClass {

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
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]);
}

new LampController();

}

}

面试技巧：不害怕，要坚强！

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