Java语言程序设计(郑莉)第八章课后习题答案.docx

Java语言程序设计第八章课后习题答案1.进程和线程有何区别，Java是如何实现多线程的。答：区别：一个程序至少有一个进程,一个进程至少有一个线程；线程的划分尺度小于进程；进程在执行过程中拥有独立的内存单元，而多个线程共享内存，从而极大地提高了程序的运行效率。Java程序一般是 继承Thread 类 或者实现 Runnable接口，从而实现多线程。2.简述线程的生命周期，重点注意线程阻塞的几种情况，以及如何重回就绪状态。答：线程的声明周期：新建-就绪-（阻塞）-运行-死亡线程阻塞的情况：休眠、进入对象wait池等待、进入对象lock池等待；休眠时间到回到就绪状态；在wait池中获得notify（）进入lock池，然后获得锁棋标进入就绪状态。3.随便选择两个城市作为预选旅游目标。实现两个独立的线程分别显示10次城市名，每次显示后休眠一段随机时间（1000毫秒以内），哪个先显示完毕，就决定去哪个城市。分别用Runnable接口和Thread类实现。（注：两个类，相同一个测试类）/Runnable接口实现的线程runable类public class runnable implements Runnable private String city; public runnable() public runnable(String city) this.city = city; public void run() for (int i = 0; i 10; i+) System.out.println(city); try /休眠1000毫秒。 Thread.sleep(1000); catch (InterruptedException e) e.printStackTrace(); / Thread类实现的线程thread类public class runnable extends Thread private String city; public runnable() public runnable(String city) this.city = city; public void run() for (int i = 0; i 10; i+) System.out.println(city); try /休眠1000毫秒。 Thread.sleep(1000); catch (InterruptedException e) e.printStackTrace(); /test8_3public class test8_3 public static void main(String args) / 将创建一个线程对象，这个对象接受一个实现了Runnable接口。实际上这里也就是使用run()方法runnable r1=new runnable(广州);runnable r2=new runnable(乌鲁木齐);Thread t1 = new Thread(r1);Thread t2 = new Thread(r2);/ 启动线程t1.start();t2.start();运行结果分别为： 4.编写一个多线程程序实现如下功能：线程A和线程B分别在屏幕上显示信息“start”后，调用wait等待；线程C开始后调用sleep休眠一段时间，然后调用notifyall，使线程A和线程B继续运行。线程A和线程B恢复运行后输出信息“end”后结束，线程C在判断线程B和线程A结束后自己结束运行。/test8_4public class test8_4 Thread A = new Thread(A) public void run() Wait(A);Thread B = new Thread(B) public void run() Wait(B);Thread C = new Thread(C) public void run() while (true) if (!A.isAlive() & !B.isAlive()return;try Thread.sleep(2000); catch (InterruptedException e) e.printStackTrace();notifyall();public synchronized void Wait(String name) System.out.println(name + .start);try wait(); catch (InterruptedException e) e.printStackTrace();System.out.println(name + .end);public synchronized void notifyall() notifyAll();public static void main(String args) test8_4 test = new test8_4();/A、B两线程一起输入start和输出end，不过中间有C让线程休眠2秒，没法全部一次性输出，/之后再唤醒，让AB继续输出下半部分endtest.A.start();test.B.start();test.C.start();运行结果：5.实现一个数据单元，包括学号和姓名两部分。编写两个线程，一个线程往数据单元中写，另一个线程往外读。要求没写一次就往外读一次。/Data类import java.util.Scanner;public class DataString studentId;String name;boolean available = false;/ 判断是读是写Scanner in = new Scanner(System.in);/ 定义一个输入对象public synchronized void read()if(available)trywait();catch(Exception e)System.out.printf(请输入学号:);trystudentId=in.next();catch(Exception e)System.out.println(输入学号出错！);System.out.printf(请输入姓名:);tryname=in.next();catch(Exception e)System.out.println(输入姓名出错！);System.out.println();available=true;notify();public synchronized void write()if(!available)trywait();catch(Exception e)System.out.println(输出学生学号：+studentId+ 姓名：+name+n);available=false;notify();/Read类public class Read extends ThreadData d1 = null;public Read(Data d)this.d1=d;public void run()while(true)d1.read();/Write类class Write extends ThreadData d2=null;public Write(Data d)this.d2=d;public void run()while(true)d2.write();/test8_5类public class test8_5 public static void main(String args)Data data=new Data();new Read(data).start();new Write(data).start();运行结果：6.创建两个不同优先级的线程，都从1数到10000，看看哪个数得快。(注：线程的优先级别越高低与执行速度没有绝对关系！)/Count类public class Count extends Thread int which;int n = 10000;public Count(int which)this.which=which;public void run() for (int i = 1; i = n; i+) if (i = n) System.out.println(which+号进程+ 结束！);/test8_6public class test8_6 public static void main(String args) Count count1 = new Count(1);Count count2 = new Count(2);Thread t1 = new Thread(count1);Thread t2 = new Thread(count2);t1.setPriority(2);/1号进程优先级是2t2.setPriority(8);/2号进程优先级是8t1.start();t2.start();运行结果： 都有可能。7.编写一个Java程序，以说明较高优先级的线程通过调用sleep方法，使较低优先级的线程获得运行的机会。（这里可以借鉴课本例813）/TestThread类public class TestThread extends Thread private int tick = 1;private int num;public TestThread(int i) this.num = i;public void run() while (tick 400000) tick+;if (tick % 50000) = 0) System.out.println(Thread # + num + ，tick = + tick);yield();try sleep(1); catch (Exception e) /test8_7public class test8_7 public static void main(String args)TestThread runners = new TestThread2;for(int i=0;i2;i+)runnersi=new TestThread(i);runners0.setPriority(2);runners1.setPriority(5);for(int i=0;i0)result=result*i;i-;*/System.out.println(the new thread of +num+is +result);System.out.println(new thread ends);/test8_8public class test8_8 public static void main(String args)System.out.println(main tread start.);SonThread newThread = new SonThread(10);newThread.start();/；浪费时间的循环int i=1;while(i=100000)i+;newThread.stop();/结束新进程System.out.println(main thread ends);运行结果：(这个结果很难把握，通常都会出现2那样的结果，知道原理就好。) 29.用两个线程模拟存、取货物。一个线程往一对象里放货物（包括品名、价格），另外一个线程取货物。分别模拟“放一个、取一个”和“放若干个、取若干个”两种情况。/Good货物类public class Good String name;int price;public Good()public Good(String name,int price)this.name=name;this.price=price;public Good(Good g)this.name=g.name;this.price=g.price;/WareHouse仓库类import java.util.ArrayList;import java.util.List;import java.util.Scanner;public class WareHouse Good good = null;Scanner in = new Scanner(System.in);List list = new ArrayList();/用来存放商品对象int count;/想存入商品的个数boolean available = true;public WareHouse() public WareHouse(int count) this.count = count;public WareHouse(List list) this.count = count;for (int i = 0; i list.size(); i+) this.list.add(Good) list.get(i);public synchronized void saveGood() if (available=false) try wait(); catch (InterruptedException e) / TODO Auto-generated catch blocke.printStackTrace();for (int i = 0; i count; i+) String n;int p;System.out.println(请输入 + (i+1) + 号商品的名称：);n = in.next();System.out.println(价格：);p = in.nextInt();good = new Good(n, p);list.add(good);available = false;notify();public synchronized void takeGood() if (available=true) try wait(); catch (InterruptedException e) / TODO Auto-generated catch blocke.printStackTrace();for (int i = 0; i list.size(); i+) good = (Good) list.get(i);System.out.print(i+1)+ 号商品的名称为： + good.name);System.out.println(t价格为： + good.price);available = true;notify();/Save存货物类public class Save extends ThreadWareHouse wareHouse = null;public Save(WareHouse w)this.wareHouse=w;public void run()wareHouse.saveGood();/Take取货物类public class Take extends ThreadWareHouse wareHouse = null;public Take(WareHouse w)this.wareHouse=w;public void run()wareHouse.takeGood();/test8_9测试类import java.util.Scanner;public class test8_9 public static void main(String args)Scanner in =new Scanner(System.in);System.out.println(请输入仓库的容量：);int i=in.nextInt();WareHouse wareHouse=new WareHouse(i);Thread saveGood=new Save(wareHouse);Thread takeGood=new Take(wareHouse);saveGood.start();takeGood.start();运行结果： 10.用两个线程模拟对话，任何一个线程都可以随时收发信息。(这道题本人搞不清楚，暂且用网上的给大家参考下。听说要用到：Socket.getInputStream()获取输入流用于“接收”Socket.getOutputStream()获取输出流用于“发送”)/test8_10import java.io.*;import java.net.*;import java.util.*;public class test8_10 public static void main(String args) try / establish server socket ServerSocket s = new ServerSocket(8189); / wait for client connection Socket incoming = s.accept(); try InputStream inStream = incoming.getInputStream(); OutputStream outStream = incoming.getOutputStream(); Scanner in = new Scanner(inStream); PrintWriter out = new PrintWriter(outStream, true); out.println(Hello! Enter BYE to exit.); / echo client input boolean done = false; while (!done & in.hasNextLine() String line = in.nextLine(); out.println(Echo: + line); if (line.trim().equals(BYE) done = true; finally incoming.close(); catch (IOException e) e.printStackTrace();