(完整word版)Java語(yǔ)言程序設(shè)計(jì)(鄭莉)第八章課后習(xí)題答案

Java語(yǔ)言程序設(shè)計(jì)第八章課后習(xí)題答案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(guò)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(jiǎn)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lock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(cè)試類）//Runnable接口實(shí)現(xiàn)的線程runable類publicclassrunnableimplementsRunnable{privateStringcity;publicrunnable(){}publicrunnable(Stringcity){this.city=city;}publicvoidrun(){for(inti=0;i<10;i++){System.out.println(city);try{//休眠1000毫秒。Thread.sleep(1000);}catch(InterruptedExceptione){e.printStackTrace();}}}}//Thread類實(shí)現(xiàn)的線程thread類publicclassrunnableextendsThread{privateStringcity;publicrunnable(){}publicrunnable(Stringcity){this.city=city;}publicvoidrun(){for(inti=0;i<10;i++){System.out.println(city);try{//休眠1000毫秒。Thread.sleep(1000);}catch(InterruptedExceptione){e.printStackTrace();}}}}//test8_3publicclasstest8_3{publicstaticvoidmain(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runnabler1=newrunnable("廣州");runnabler2=newrunnable("烏魯木齊");Threadt1=newThread(r1);Threadt2=newThread(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(kāi)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_4publicclasstest8_4{ThreadA=newThread("A"){publicvoidrun(){Wait("A");}};ThreadB=newThread("B"){publicvoidrun(){Wait("B");}};ThreadC=newThread("C"){publicvoidrun(){while(true){if(!A.isAlive()&&!B.isAlive())return;try{Thread.sleep(2000);}catch(InterruptedExceptione){e.printStackTrace();}notifyall();}}};publicsynchronizedvoidWait(Stringname){System.out.println(name+"..start");try{wait();}catch(InterruptedExceptione){e.printStackTrace();}System.out.println(name+"..end");}publicsynchronizedvoidnotifyall(){notifyAll();}publicstaticvoidmain(Stringargs[]){test8_4test=newtest8_4();//A、B兩線程一起輸入start和輸出end，不過(guò)中間有C讓線程休眠2秒，沒(méi)法全部一次性輸出，//之后再喚醒，讓AB繼續(xù)輸出下半部分endtest.A.start();test.B.start();test.C.start();}}運(yùn)行結(jié)果：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(méi)寫一次就往外讀一次。//Data類importjava.util.Scanner;publicclassData{StringstudentId;Stringname;booleanavailable=false;//判斷是讀是寫Scannerin=newScanner(System.in);//定義一個(gè)輸入對(duì)象publicsynchronizedvoidread(){if(available)try{wait();}catch(Exceptione){}System.out.printf("請(qǐng)輸入學(xué)號(hào):");try{studentId=in.next();}catch(Exceptione){System.out.println("輸入學(xué)號(hào)出錯(cuò)！");}System.out.printf("請(qǐng)輸入姓名:");try{name=in.next();}catch(Exceptione){System.out.println("輸入姓名出錯(cuò)！");}System.out.println();available=true;notify();}publicsynchronizedvoidwrite(){if(!available)try{wait();}catch(Exceptione){}System.out.println("輸出學(xué)生學(xué)號(hào)："+studentId+"姓名："+name+"\n");available=false;notify();}}//Read類publicclassReadextendsThread{Datad1=null;publicRead(Datad){this.d1=d;}publicvoidrun(){while(true){d1.read();}}}//Write類classWriteextendsThread{Datad2=null;publicWrite(Datad){this.d2=d;}publicvoidrun(){while(true){d2.write();}}}//test8_5類publicclasstest8_5{publicstaticvoidmain(String[]args){Datadata=newData();newRead(data).start();newWrite(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(méi)有絕對(duì)關(guān)系！)//Count類publicclassCountextendsThread{intwhich;intn=10000;publicCount(intwhich){this.which=which;}publicvoidrun(){for(inti=1;i<=n;i++){if(i==n){System.out.println(which+"號(hào)進(jìn)程"+"結(jié)束！");}}}}//test8_6publicclasstest8_6{publicstaticvoidmain(String[]args){Countcount1=newCount(1);Countcount2=newCount(2);Threadt1=newThread(count1);Threadt2=newThread(count2);t1.setPriority(2);//1號(hào)進(jìn)程優(yōu)先級(jí)是2t2.setPriority(8);//2號(hào)進(jìn)程優(yōu)先級(jí)是8t1.start();t2.start();}}運(yùn)行結(jié)果：都有可能。7.編寫一個(gè)Java程序，以說(shuō)明較高優(yōu)先級(jí)的線程通過(guò)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publicclassTestThreadextendsThread{privateinttick=1;privateintnum;publicTestThread(inti){this.num=i;}publicvoidrun(){while(tick<400000){tick++;if((tick%50000)==0){System.out.println("Thread#"+num+"，tick="+tick);yield();try{sleep(1);}catch(Exceptione){}}}}}//test8_7publicclasstest8_7{publicstaticvoidmain(String[]args){TestThread[]runners=newTestThread[2];for(inti=0;i<2;i++){runners[i]=newTestThread(i);}runners[0].setPriority(2);runners[1].setPriority(5);for(inti=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)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publicclassSonThreadextendsThread{privateintnum;publicSonThread(intnum){this.num=num;}publicvoidrun(){inti=num;intresult=1;System.out.println("newthreadstart.");/*while(i>0){result=result*i;i--;}*/System.out.println("thenewthreadof"+num+"is"+result);System.out.println("newthreadends");}}//test8_8publicclasstest8_8{publicstaticvoidmain(String[]args){System.out.println("maintreadstart.");SonThreadnewThread=newSonThread(10);newThread.start();//；浪費(fèi)時(shí)間的循環(huán)inti=1;while(i<=100000){i++;}newThread.stop();//結(jié)束新進(jìn)程System.out.println("mainthreadends");}}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。)29.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publicclassGood{Stringname;intprice;publicGood(){}publicGood(Stringname,intprice){=name;this.price=price;}publicGood(Goodg){=;this.price=g.price;}}//WareHouse倉(cāng)庫(kù)類importjava.util.ArrayList;importjava.util.List;importjava.util.Scanner;publicclassWareHouse{Goodgood=null;Scannerin=newScanner(System.in);Listlist=newArrayList();//用來(lái)存放商品對(duì)象intcount;//想存入商品的個(gè)數(shù)booleanavailable=true;publicWareHouse(){}publicWareHouse(intcount){this.count=count;}publicWareHouse(Listlist){this.count=count;for(inti=0;i<list.size();i++){this.list.add((Good)list.get(i));}}publicsynchronizedvoidsaveGood(){if(available==false){try{wait();}catch(InterruptedExceptione){//TODOAuto-generatedcatchblocke.printStackTrace();}}for(inti=0;i<count;i++){Stringn;intp;System.out.println("請(qǐng)輸入"+(i+1)+"號(hào)商品的名稱：");n=in.next();System.out.println("價(jià)格：");p=in.nextInt();good=newGood(n,p);list.add(good);}available=false;notify();}publicsynchronizedvoidtakeGood(){if(available==true){try{wait();}catch(InterruptedExceptione){//TODOAuto-generatedcatchblocke.printStackTrace();}}for(inti=0;i<list.size();i++){good=(Good)list.get(i);System.out.print((i+1)+"號(hào)商品的名稱為："+);System.out.println("\t價(jià)格為："+good.price);}available=true;notify();}}//Save存貨物類publicclassSaveextendsThread{WareHousewareHouse=null;publicSave(WareHousew){this.wareHouse=w;}publicvoidrun(){wareHouse.saveGood();}}//Take取貨物類publicclassTakeextendsThread{WareHousewareHouse=null;publicTake(WareHousew){this.wareHouse=w;}publicvoidrun(){wareHouse.takeGood();}}//test8_9測(cè)試類importjava.util.Scanner;publicclasstest8_9{publicstaticvoidmain(String[]args){Scannerin=newScanner(System.in);System.out.println("請(qǐng)輸入倉(cāng)庫(kù)的容量：");inti=in.nextInt();WareHousewareHouse=newWareHouse(i);ThreadsaveGood=newSave(wareHouse);ThreadtakeGood=newTake(wareHouse);saveGood.start();takeGood.start();}}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