java第八章答案

《java第八章答案》由會(huì)員分享，可在線閱讀，更多相關(guān)《java第八章答案（16頁珍藏版）》請?jiān)谘b配圖網(wǎng)上搜索。

1、1.進(jìn)程和線程有何區(qū)別，Java是如何實(shí)現(xiàn)多線程的。 答：區(qū)別：一個(gè)程序至少有一個(gè)進(jìn)程,一個(gè)進(jìn)程至少有一個(gè)線程；線程的劃分尺度小于進(jìn)程；進(jìn)程在執(zhí)行過程中擁有獨(dú)立的內(nèi)存單元，而多個(gè)線程共享內(nèi)存，從而極大地提高了程序的運(yùn)行效率。 Java程序一般是 繼承Thread 類 或者實(shí)現(xiàn) Runnable接口，從而實(shí)現(xiàn)多線程。 2.簡述線程的生命周期，重點(diǎn)注意線程阻塞的幾種情況，以及如何重回就緒狀態(tài)。 答：線程的聲明周期：新建-就緒-（阻塞）-運(yùn)行--死亡 線程阻塞的情況：休眠、進(jìn)入對(duì)象wait池等待、進(jìn)入對(duì)象lock池等待； 休眠時(shí)間到回到就緒狀態(tài)；在wait池中獲得notify（）進(jìn)入lo

2、ck池，然后獲得鎖棋標(biāo)進(jìn)入就緒狀態(tài)。 3.隨便選擇兩個(gè)城市作為預(yù)選旅游目標(biāo)。實(shí)現(xiàn)兩個(gè)獨(dú)立的線程分別顯示10次城市名，每次顯示后休眠一段隨機(jī)時(shí)間（1000毫秒以內(nèi)），哪個(gè)先顯示完畢，就決定去哪個(gè)城市。分別用Runnable接口和Thread類實(shí)現(xiàn)。 （注：兩個(gè)類，相同一個(gè)測試類） //Runnable接口實(shí)現(xiàn)的線程runable類 public class runnable implements Runnable { ?private String city; ?public runnable() {} ?public runnable(String city) { ? this

3、.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類實(shí)現(xiàn)的線程thread類 public class runnable extends

4、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.

5、printStackTrace(); ?? } ? }? ?} ?} ? //test8_3 public class test8_3 { ?public static void main(String[] args) { ??// 將創(chuàng)建一個(gè)線程對(duì)象，這個(gè)對(duì)象接受一個(gè)實(shí)現(xiàn)了Runnable接口。實(shí)際上這里也就是使用run()方法 ??runnable r1=new runnable("廣州"); ??runnable r2=new runnable("烏魯木齊"); ??Thread t1 = new Thread(r1); ??Thread t2 = new T

6、hread(r2); ??// 啟動(dòng)線程 ??t1.start(); ??t2.start(); ?} } 運(yùn)行結(jié)果分別為： ??? 4.編寫一個(gè)多線程程序?qū)崿F(xiàn)如下功能：線程A和線程B分別在屏幕上顯示信息“…start”后，調(diào)用wait等待；線程C開始后調(diào)用sleep休眠一段時(shí)間，然后調(diào)用notifyall，使線程A和線程B繼續(xù)運(yùn)行。線程A和線程B恢復(fù)運(yùn)行后輸出信息“…end”后結(jié)束，線程C在判斷線程B和線程A結(jié)束后自己結(jié)束運(yùn)行。 //test8_4 public class test8_4 { ?Thread A = new Thread("A") {

7、 ??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); ????} ca

8、tch (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

9、(name + "..end"); ?} ?public synchronized void notifyall() { ??notifyAll(); ?} ?public static void main(String args[]) { ??test8_4 test = new test8_4(); ??//A、B兩線程一起輸入start和輸出end，不過中間有C讓線程休眠2秒，沒法全部一次性輸出， ??//之后再喚醒，讓AB繼續(xù)輸出下半部分end ??test.A.start(); ??test.B.start(); ??test.C.start(); ?} }

10、 運(yùn)行結(jié)果： ? 4. lass test implements Runnable{ public test(){ } public void run(){ if(Thread.currentThread().getName().equals("A")){ System.out.println("A...start"); synchronized(this) { try{ wait(); System.out.println("A...end"); notify(); }catch(Exception e){

11、 } } } else if(Thread.currentThread().getName().equals("B")){ System.out.println("B...start"); synchronized(this){ try{ wait(); System.out.println("B...end"); }catch(Exception e){ } } }else if(Thread.currentThread().getName().equals("C")){ try{ Thread.sleep(10);

12、 synchronized(this){ notify(); } }catch(Exception e){ } } } } public class d { public static void main(String args[]) { test show=new test(); Thread A=new Thread(show,"A"); Thread B=new Thread(show,"B"); Thread C=new Thread(show,"C"); A.start(); B.start(); C.start()

13、; } } 5.實(shí)現(xiàn)一個(gè)數(shù)據(jù)單元，包括學(xué)號(hào)和姓名兩部分。編寫兩個(gè)線程，一個(gè)線程往數(shù)據(jù)單元中寫，另一個(gè)線程往外讀。要求沒寫一次就往外讀一次。 //Data類 import java.util.Scanner; public class Data{ ?String studentId; ?String name; ?boolean available = false;// 判斷是讀是寫 ?Scanner in = new Scanner(System.in);// 定義一個(gè)輸入對(duì)象 ?public synchronized void read() ?{ ?

14、?if(available) ???try ???{ ????wait(); ???} ???catch(Exception e) ???{ ???? ???} ??System.out.printf("請輸入學(xué)號(hào):"); ??try ??{ ???studentId=in.next(); ??} ??catch(Exception e) ??{ ???System.out.println("輸入學(xué)號(hào)出錯(cuò)！"); ??} ??System.out.printf("請輸入姓名:"); ??try ??{ ???name=in.next(); ??}

15、??catch(Exception e) ??{ ???System.out.println("輸入姓名出錯(cuò)！"); ??} ??System.out.println(); ??available=true; ??notify(); ?} ?public synchronized void write() ?{ ??if(!available) ???try ???{ ????wait(); ???} ???catch(Exception e) ???{??? ???} ??System.out.println("輸出學(xué)生學(xué)號(hào)："+studentId+" 姓

16、名："+name+"\n"); ??available=false; ??notify(); ?} } //Read類 public class Read extends Thread{ ?Data d1 = null; ?public Read(Data d){ ??this.d1=d;? ?} ?public void run(){ ??while(true) ??{ ???d1.read(); ??} ?} } //Write類 class Write extends Thread{ ?Data d2=null; ?public Write(Da

17、ta d) ?{ ??this.d2=d; ?} ?public void run() ?{ ??while(true) ??{ ???d2.write(); ??} ?} } //test8_5類 public class test8_5 { ?public static void main(String[] args){ ??Data data=new Data(); ??new Read(data).start(); ??new Write(data).start(); ?? ?} } 運(yùn)行結(jié)果： ? 6.創(chuàng)建兩個(gè)不同優(yōu)先級(jí)的線程，都

18、從1數(shù)到10000，看看哪個(gè)數(shù)得快。 (注：線程的優(yōu)先級(jí)別越高低與執(zhí)行速度沒有絕對(duì)關(guān)系！) //Count類 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+"號(hào)進(jìn)程"+ "結(jié)束！"); ???

19、} ??} ?} } //test8_6 public 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號(hào)進(jìn)程優(yōu)先級(jí)是2 ??t2.setPriority(8);//2號(hào)進(jìn)程優(yōu)先級(jí)是8 ??t1

20、.start(); ??t2.start(); ?} } 運(yùn)行結(jié)果： 都有可能。 7.編寫一個(gè)Java程序，以說明較高優(yōu)先級(jí)的線程通過調(diào)用sleep方法，使較低優(yōu)先級(jí)的線程獲得運(yùn)行的機(jī)會(huì)。 （這里可以借鑒課本例8—13） //TestThread類 public class TestThread extends Thread { ?private int tick = 1; ?private int num; ?public TestThread(int i) { ??this.num = i; ?} ?public void run() { ??while

21、 (tick < 400000) { ???tick++; ???if ((tick % 50000) == 0) { ????System.out.println("Thread #" + num + "，tick =" + tick); ????yield(); ????try { ?????sleep(1); ????} catch (Exception e) { ????} ???} ??} ?} } //test8_7 public class test8_7 { ?public static void main(String[] args){ ??T

22、estThread[] runners = new TestThread[2]; ??for(int i=0;i<2;i++){ ???runners[i]=new TestThread(i); ??} ??runners[0].setPriority(2); ??runners[1].setPriority(5); ??for(int i=0;i<2;i++){ ???runners[i].start(); ??} ? ?} } 運(yùn)行結(jié)果： ? 8.主線程控制新線程的生命，當(dāng)主線程運(yùn)行一段時(shí)間后，控制新線程死亡，主線程繼續(xù)運(yùn)行一段時(shí)間后結(jié)束。 (注：main函數(shù)

23、就是主線程，程序里其他的Thread都屬于子線程。可以參考課本的例8—1) //SonThread類 public class SonThread extends Thread{ ?private int num; ?public SonThread(int num){ ??this.num=num; ?} ?public void run(){ ??int i=num; ??int result=1; ??System.out.println("new thread start."); ?/*?while(i>0){ ???result=result*i; ???i

24、--; ??}*/ ??System.out.println("the new thread of "+num+"is "+result); ??System.out.println("new thread ends"); ?} } //test8_8 public class test8_8 { ?public static void main(String[] args){ ??System.out.println("main tread start."); ??SonThread newThread = new SonThread(10); ??newThread.

25、start(); ??//；浪費(fèi)時(shí)間的循環(huán) ??int i=1; ??while(i<=100000){ ???i++; ??} ??newThread.stop();//結(jié)束新進(jìn)程 ??System.out.println("main thread ends"); ?? ?} } 運(yùn)行結(jié)果：(這個(gè)結(jié)果很難把握，通常都會(huì)出現(xiàn)2那樣的結(jié)果，知道原理就好。) 2 ? 9.用兩個(gè)線程模擬存、取貨物。一個(gè)線程往一對(duì)象里放貨物（包括品名、價(jià)格），另外一個(gè)線程取貨物。分別模擬“放一個(gè)、取一個(gè)”和“放若干個(gè)、取若干個(gè)”兩種情況。 //Good貨物類 public cla

26、ss 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倉庫類 import java.util.ArrayList; import java.util.List; import jav

27、a.util.Scanner; public class WareHouse { ?Good good = null; ?Scanner in = new Scanner(System.in); ?List list = new ArrayList();//用來存放商品對(duì)象 ?int count;//想存入商品的個(gè)數(shù) ?boolean available = true; ?public WareHouse() { ?} ? ?public WareHouse(int count) { ??this.count = count; ?} ?public WareHouse

28、(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 block ??

29、??e.printStackTrace(); ???} ??}?? ??for (int i = 0; i < count; i++) { ???String n; ???int p; ???System.out.println("請輸入" + (i+1) + "號(hào)商品的名稱："); ???n = in.next(); ???System.out.println("價(jià)格："); ???p = in.nextInt(); ???good = new Good(n, p); ???list.add(good); ??} ??available = false; ??no

30、tify();???? ?} ?public synchronized void takeGood() { ??if (available==true) { ???try { ????wait(); ???} catch (InterruptedException e) { ????// TODO Auto-generated catch block ????e.printStackTrace(); ???} ??} ??for (int i = 0; i < list.size(); i++) { ???good = (Good) list.get(i); ???S

31、ystem.out.print((i+1)+ "號(hào)商品的名稱為：" + good.name); ???System.out.println("\t價(jià)格為：" + good.price); ??} ??available = true; ??notify(); ?} } //Save存貨物類 public class Save extends Thread{ ?WareHouse wareHouse = null; ?public Save(WareHouse w){ ??this.wareHouse=w;? ?} ?public void run(){ ?? ??

32、?wareHouse.saveGood();?? ?} } //Take取貨物類 public class Take extends Thread{ ?WareHouse wareHouse = null; ?public Take(WareHouse w){ ??this.wareHouse=w;? ?} ?public void run(){?? ?? ???wareHouse.takeGood();?????? ?} } //test8_9測試類 import java.util.Scanner; public class test8_9 { ?publ

33、ic static void main(String[] args){?? ??Scanner in =new Scanner(System.in); ??System.out.println("請輸入倉庫的容量："); ??int i=in.nextInt(); ??WareHouse wareHouse=new WareHouse(i); ??Thread saveGood=new Save(wareHouse); ??Thread takeGood=new Take(wareHouse); ? ??saveGood.start(); ??takeGood.start()

34、;????? ?} } 運(yùn)行結(jié)果：? 10.用兩個(gè)線程模擬對(duì)話，任何一個(gè)線程都可以隨時(shí)收發(fā)信息。 (這道題本人搞不清楚，暫且用網(wǎng)上的給大家參考下。 聽說要用到： Socket.getInputStream()獲取輸入流用于“接收” Socket.getOutputStream()獲取輸出流用于“發(fā)送” ) //test8_10 import java.io.*; import .*; import java.util.*; public class test8_10 { ??? public static void main(String[] args

35、) { ??????? try { ??????????? // establish server socket ??????????? ServerSocket s = new ServerSocket(8189); ??????????? // wait for client connection ??????????? Socket incoming = s.accept(); ??????????? try { ??????????????? InputStream inStream = incoming.getInputStream(); ??????????????

36、? 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 d

37、one = 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(); ??????? } ??? } }