《lecture7.javathreads》

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1、Lecture7.JavaThreadsCheng-ChiaChenContentsWhatisathread?DefineandlaunchathreadThelife-cycleofathreadinterruptathreadthreadsynchronizationotherissuesWhatisathread?Asequential(orsingle-threaded)programisonethat,whenexecuted,hasonlyonesingleflowofcontrol.i.e.,atanytimeinstant,thereisat

2、mostonlyoneinstruction(orstatementorexecutionpoint)thatisbeingexecutedintheprogram.Amulti-threadedprogramisonethatcanhavemultipleflowsofcontrolwhenexecuted.Atsometimeinstance,theremayexistmultipleinstructionsorexecutionpoints)thatarebeingexecutedintheprogramEx:inaWebbrowserwemaydothe

3、followingtasksatthesametime:1.scrollapage,2.downloadanappletorimage,3.playsound,4printapage.Athreadisasinglesequentialflowofcontrolwithinaprogram.single-threadedvsmultithreadedprograms{A();A1();A2();A3();B1();B2();}{A();newThreads{{A1();A2();A3()};{B1();B2()}}}startedbyjavafrommain(S

4、tring[])startedbymainthreadstartedbyBthreadlifetimeofCthreadThreadecologyinajavaprogram2.DefineandlaunchajavathreadEachJavaRuntimethreadisencapsulatedinajava.lang.Threadinstance.Twowaystodefineathread:1.ExtendtheThreadclass2.ImplementtheRunnableinterface:packagejava.lang;publicinterf

5、aceRunnable{publicvoidrun();}StepsforextendingtheThreadclass:SubclasstheThreadclass;OverridethedefaultThreadmethodrun(),whichistheentrypointofthethread,likethemain(String[])methodinajavaprogram.Defineathread//Example:publicclassPrint2ConsoleextendsThread{publicvoidrun(){//run()istoat

6、hreadwhatmain()istoajavaprogramfor(intb=-128;b<128;b++)out.println(b);}…//additionalmethods,fields…}ImpementtheRunnableinterfaceifyouneedaparentclass://byextendingJTextAreawecanreuseallexistingcodeofJTextAreapublicclassPrinter2GUIextendJTextAreaimplementRunnable{publicvoidrun(){for(i

7、ntb=-128;b<128;b++)append(Integer.toString(b)+“”);}}Howtolaunchathreadcreateaninstanceof[asubclassof]ofThread,saythread.Threadthread=newPrint2Console();Threadthread=newThread(newPrint2GUI(..));2.callitsstart()method,thread.start();.//note:notcallrun()!!Ex:Printer2Consolet1=newPrint

8、2Console();/