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java多线程总结（二）

發(fā)布時(shí)間：2025/3/8 编程问答 18 豆豆

生活随笔收集整理的這篇文章主要介紹了 java多线程总结（二）小編覺(jué)得挺不錯(cuò)的,現(xiàn)在分享給大家,幫大家做個(gè)參考.

線程一般有6個(gè)狀態(tài)：

新建狀態(tài)：NEW

可運(yùn)行狀態(tài)：RUNNABLE

休眠狀態(tài)：TIMED_WAITING

等待狀態(tài)：WAITING

阻塞狀態(tài):BLOCKED

終止?fàn)顟B(tài)“TERMINATED

當(dāng)我們使用new創(chuàng)建線程之后，線程處于新建狀態(tài)，當(dāng)調(diào)用start方法之后，線程出于可運(yùn)行狀態(tài)，當(dāng)線程需要獲得對(duì)象的內(nèi)置鎖，而這個(gè)鎖被其他線程所占用的時(shí)候，線程就出于阻塞狀態(tài)，當(dāng)線程等待其他線程通知調(diào)度表可以運(yùn)行時(shí)，線程處于等待狀態(tài)，當(dāng)一個(gè)含有時(shí)間參數(shù)的方法，必須sleep（）方法，可以讓線程處于計(jì)時(shí)等待狀態(tài)，當(dāng)run（）方法運(yùn)行完畢或者出現(xiàn)異常，線程處于終止?fàn)顟B(tài)。

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package?Thread; public?class?ThreadStateDemo{ ????public?static?void?main(String[] args)?throws?Exception{ ????????ThreadState state =?new?ThreadState(); ????????Thread demo =?new?Thread(state); ????????System.out.println("新建狀態(tài)："?+ demo.getState()); ????????demo.start(); ????????System.out.println("可運(yùn)行狀態(tài)："?+ demo.getState()); ????????Thread.sleep(100); ????????System.out.println("休眠狀態(tài)："?+ demo.getState()); ????????Thread.sleep(1000); ????????System.out.println("等待狀態(tài)："?+ demo.getState()); ????????state.notifyWait(); ????????System.out.println("阻塞狀態(tài):"?+ demo.getState()); ????????Thread.sleep(1000); ????????System.out.println("終止?fàn)顟B(tài)“"?+ demo.getState()); ????} } class?ThreadState?implements?Runnable{ ????@Override ????public?void?run(){ ????????try{ ????????????waitForASecond(); ????????????waitForAYear(); ????????}catch(Exception e){ ????????????e.printStackTrace(); ????????} ????} ????// 當(dāng)前線程等待1秒 ????public?synchronized?void?waitForASecond()?throws?Exception{ ????????wait(1000); ????} ????// 當(dāng)前線程一直等待 ????public?synchronized?void?waitForAYear()?throws?Exception{ ????????wait(); ????} ????// 喚醒線程 ????public?synchronized?void?notifyWait()?throws?Exception{ ????????notify(); ????} }

【運(yùn)行結(jié)果】：

新建狀態(tài)：NEW

可運(yùn)行狀態(tài)：RUNNABLE

休眠狀態(tài)：TIMED_WAITING

等待狀態(tài)：WAITING

阻塞狀態(tài):BLOCKED

終止?fàn)顟B(tài)“TERMINATED

線程組表示一個(gè)線程線程的集合，線程組中也可以包含其他的線程組。線程組構(gòu)成一棵樹(shù)。

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package?Thread; import?java.util.ArrayList; import?java.util.List; public?class?ThreadGroupDemo{ ????public?static?void?main(String[] args){ ????????for(String str : getThreadGroups(GetRootThreadGroups())){ ????????????System.out.println(str); ????????} ????} ????// 獲得根線程組 ????private?static?ThreadGroup GetRootThreadGroups(){ ????????// 獲得當(dāng)前的線程組 ????????ThreadGroup rootGroup = Thread.currentThread().getThreadGroup(); ????????while(true){ ????????????if(rootGroup.getParent() !=?null){ ????????????????rootGroup = rootGroup.getParent(); ????????????}else{ ????????????????break; ????????????} ????????} ????????return?rootGroup; ????} ????// 獲得給定線程組中所有線程名 ????public?static?List<String> getThreads(ThreadGroup group){ ????????List<String> threadList =?new?ArrayList<String>(); ????????Thread[] threads =?new?Thread[group.activeCount()]; ????????int?count = group.enumerate(threads,?false); ????????for(int?i =?0; i < count; i++){ ????????????threadList.add(group.getName() +?" 線程組 "?+ threads[i].getName()); ????????} ????????return?threadList; ????} ????// 獲得線程組中所有子線程組 ????public?static?List<String> getThreadGroups(ThreadGroup group){ ????????List<String> threadList = getThreads(group); ????????ThreadGroup[] groups =?new?ThreadGroup[group.activeGroupCount()]; ????????int?count = group.enumerate(groups,?false); ????????for(int?i =?0; i < count; i++){ ????????????threadList.addAll(getThreads(groups[i])); ????????} ????????return?threadList; ????} }

【運(yùn)行結(jié)果】：

system?線程組?Reference Handler

system?線程組?Finalizer

system?線程組?Signal Dispatcher

system?線程組?Attach Listener

main?線程組?main

使用守護(hù)線程

java中的線程分為2類(lèi)，用戶(hù)線程和守護(hù)線程，守護(hù)線程主要為其他線程提供服務(wù)，守護(hù)線程會(huì)隨時(shí)被中斷，所以一般不要再守護(hù)線程中使用需要釋放資源的資源，比如輸入輸出流等，守護(hù)線程一般都是后臺(tái)線程，如果虛擬機(jī)只剩下守護(hù)線程，虛擬機(jī)就會(huì)退出。

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package?Thread; public?class?DaemonThreadTest{ ????public?static?void?main(String[] args){ ????????Thread worker =?new?Thread(new?Worker()); ????????Thread timer =?new?Thread(new?Timer()); ????????//設(shè)置守護(hù)線程 ????????timer.setDaemon(true); ????????worker.start(); ????????timer.start(); ????} } class?Worker?implements?Runnable{ ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?5; ++i){ ????????????System.out.println("rollen真帥! 第"?+ i +?"次"); ????????} ????} } class?Timer?implements?Runnable{ ????@Override ????public?void?run(){ ????????long?currentTime = System.currentTimeMillis(); ????????long?processTime =?0; ????????while(true){ ????????????if((System.currentTimeMillis() - currentTime) > processTime){ ????????????????processTime = System.currentTimeMillis() - currentTime; ????????????????System.out.println("程序運(yùn)行時(shí)間："?+ processTime); ????????????} ????????} ????} }

rollen真帥!?第0次

程序運(yùn)行時(shí)間：1

程序運(yùn)行時(shí)間：2

程序運(yùn)行時(shí)間：3

程序運(yùn)行時(shí)間：4

程序運(yùn)行時(shí)間：5

rollen真帥!?第1次

rollen真帥!?第2次

rollen真帥!?第3次

rollen真帥!?第4次

程序運(yùn)行時(shí)間：6

終止指定的線程

雖然在Thread類(lèi)中提供了stop（）方法可以終止線程，但是由于其固有的不安全性，所以一般不要采用，本例子只是起到拋磚引玉的作用。

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package?Thread; import?java.awt.FlowLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; public?class?ThreadStopDemo?extends?JFrame{ ????public?ThreadStopDemo(){ ????????panel.setLayout(new?FlowLayout(FlowLayout.CENTER)); ????????panel.add(label); ????????panel.add(startButton); ????????panel.add(endButton); ????????setContentPane(panel); ????????setSize(200,?300); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????????startButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????counter =?new?CounterThread(); ????????????????new?Thread(counter).start(); ????????????} ????????}); ????????endButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????if(counter ==?null){ ????????????????????return; ????????????????} ????????????????counter.setStop(false); ????????????} ????????}); ????} ????public?static?void?main(String[] args){ ????????new?ThreadStopDemo(); ????} ????class?CounterThread?implements?Runnable{ ????????@Override ????????public?void?run(){ ????????????while(this.flag){ ????????????????try{ ????????????????????Thread.sleep(500); ????????????????}catch(Exception e){ ????????????????????e.printStackTrace(); ????????????????} ????????????????label.setText("更新"?+ (count++) +?"更新"); ????????????} ????????} ????????public?void?setStop(boolean?flag){ ????????????this.flag = flag; ????????} ????????private?int?count =?0; ????????private?boolean?flag =?true; ????} ????private?CounterThread counter =?null; ????private?final?JPanel panel =?new?JPanel(); ????private?final?JLabel label =?new?JLabel("更新0次"); ????private?final?JButton startButton =?new?JButton("開(kāi)始"); ????private?final?JButton endButton =?new?JButton("結(jié)束"); }

【運(yùn)行結(jié)果】：

線程的插隊(duì)

在編寫(xiě)多線程的程序的時(shí)候，經(jīng)常會(huì)遇到讓一個(gè)線程優(yōu)先于另外i個(gè)線程運(yùn)行的情況，此時(shí)，除了設(shè)置這個(gè)線程的優(yōu)先級(jí)高（不推薦這種方法）之外，更加直接的辦法是采用Thread類(lèi)中的join（）方法。當(dāng)插隊(duì)的線程運(yùn)行結(jié)束之后，其他的線程才能運(yùn)行。

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package?Thread; public?class?ThreadJoinDemo{ ????public?static?void?main(String[] args){ ????????Thread demo1 =?new?Thread(new?EmergencyThread()); ????????demo1.start(); ????????for(int?i =?0; i <?5; ++i){ ????????????try{ ????????????????Thread.sleep(100); ????????????}catch(InterruptedException e){ ????????????????e.printStackTrace(); ????????????} ????????????System.out.println("正常情況 :"?+ i +?"號(hào)車(chē)開(kāi)始出發(fā)"); ????????????try{ ????????????????//開(kāi)始插隊(duì) ????????????????demo1.join(); ????????????}catch(InterruptedException e){ ????????????????e.printStackTrace(); ????????????} ????????} ????} } class?EmergencyThread?implements?Runnable{ ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?5; ++i){ ????????????try{ ????????????????Thread.sleep(100); ????????????}catch(InterruptedException e){ ????????????????e.printStackTrace(); ????????????} ????????????System.out.println("緊急情況："?+ i +?"號(hào)車(chē)開(kāi)始出發(fā)"); ????????} ????} }

【運(yùn)行結(jié)果】：

正常情況?:0號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：0號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：1號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：2號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：3號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：4號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:1號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:2號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:3號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:4號(hào)車(chē)開(kāi)始出發(fā)

如果我們?nèi)サ鬸oin哪一行的話，運(yùn)行結(jié)果：（結(jié)果不唯一）

緊急情況：0號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:0號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：1號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:1號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:2號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：2號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：3號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:3號(hào)車(chē)開(kāi)始出發(fā)

正常情況?:4號(hào)車(chē)開(kāi)始出發(fā)

緊急情況：4號(hào)車(chē)開(kāi)始出發(fā)

線程的同步

多線程編程的一個(gè)重要原因是實(shí)現(xiàn)數(shù)據(jù)的共享，但是如果兩個(gè)線程同時(shí)修改一個(gè)數(shù)據(jù)的話，則會(huì)產(chǎn)生同步問(wèn)題。

下面采用一個(gè)2個(gè)人同時(shí)往銀行存錢(qián)的例子，銀行卡初始金額為100元。每次存10元，大家仔細(xì)查看余額。（對(duì)于簡(jiǎn)單的多線程，出錯(cuò)的概率很小，今天很不巧，我一向地下的RP今天居然爆發(fā)了，實(shí)驗(yàn)了很多次，都沒(méi)錯(cuò)，最后終于出現(xiàn)了）

先看一下結(jié)果吧：

案例說(shuō)兩側(cè)不能出現(xiàn)一樣余額的。

代碼如下：

package?Thread; import?java.awt.GridLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; import?javax.swing.JScrollPane; import?javax.swing.JTextArea; public?class?UnSynBank?extends?JFrame{ ????public?UnSynBank(){ ????????panel.setLayout(new?GridLayout(2,?2,?3,?3)); ????????panel.add(label1); ????????panel.add(label2); ????????JScrollPane js1 =?new?JScrollPane(oneArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js1); ????????JScrollPane js2 =?new?JScrollPane(twoArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js2); ????????panel2.add(panel); ????????panel2.add(statrButton); ????????setContentPane(panel2); ????????statrButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????Thread demo1 =?new?Thread(new?Transfer(bank, oneArea)); ????????????????demo1.start(); ????????????????Thread demo2 =?new?Thread(new?Transfer(bank, twoArea)); ????????????????demo2.start(); ????????????} ????????}); ????????setSize(300,?400); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????} ????public?static?void?main(String[] args){ ????????new?UnSynBank(); ????} ????private?final?Bank bank =?new?Bank(); ????JPanel panel =?new?JPanel(); ????JPanel panel2 =?new?JPanel(); ????private?final?JButton statrButton =?new?JButton("開(kāi)始存錢(qián)"); ????private?final?JLabel label1 =?new?JLabel("一號(hào)線程"); ????private?final?JLabel label2 =?new?JLabel("二號(hào)線程"); ????private?final?JTextArea oneArea =?new?JTextArea(5,?10); ????private?final?JTextArea twoArea =?new?JTextArea(5,?10); } /** ?* 表示銀行的類(lèi) ?* */ class?Bank{ ????public?Bank(){ ????} ????public?void?deposit(int?money){ ????????account += money; ????} ????public?int?getAccount(){ ????????return?account; ????} ????private?int?account =?100; } /** ?* 表示往賬戶(hù)存錢(qián) ?* */ class?Transfer?implements?Runnable{ ????public?Transfer(){ ????} ????public?Transfer(Bank bank, JTextArea textArea){ ????????this.bank = bank; ????????this.textArea = textArea; ????} ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?20; ++i){ ????????????bank.deposit(10); ????????????String str = textArea.getText(); ????????????textArea.setText(str +?"賬戶(hù)余額為："?+ bank.getAccount() +?"\n"); ????????} ????} ????private?Bank bank =?null; ????private?JTextArea textArea =?null; }

因?yàn)橐粋€(gè)進(jìn)程中的所有線程會(huì)共享進(jìn)程中的資源，所以當(dāng)一個(gè)線程還沒(méi)有將修改之后的結(jié)果保存的時(shí)候，另外一個(gè)線程卻進(jìn)行讀取，這樣自然會(huì)產(chǎn)生錯(cuò)誤，所以這個(gè)時(shí)候就需要我們采用同步來(lái)解決問(wèn)題的。

使用同步方法實(shí)現(xiàn)同步

所謂同步方法，就是用synchronized修飾的方法，之所以這十幾個(gè)字母能解決困難的同步問(wèn)題，這是和java中的內(nèi)置鎖密切相關(guān)的，每一個(gè)java對(duì)象中有一個(gè)內(nèi)置鎖，如果方法使用了synchronized進(jìn)行修飾的話，內(nèi)置鎖會(huì)保護(hù)整個(gè)方法，也就是在調(diào)用方法之前，需要、獲得內(nèi)置鎖，否則就會(huì)處于阻塞狀態(tài)，當(dāng)然這個(gè)關(guān)鍵字也可以修飾靜態(tài)方法，如果調(diào)用靜態(tài)方法，就會(huì)鎖住整個(gè)類(lèi)

但是要提醒一下大家，同步是一種高開(kāi)銷(xiāo)的操作，所以應(yīng)該盡量減少需要同步的內(nèi)容

使用特殊域變量實(shí)現(xiàn)同步

volatile提供了一種免鎖的機(jī)制，使用這個(gè)關(guān)鍵字修飾的域相當(dāng)于告訴虛擬機(jī)，這個(gè)域可能會(huì)被其他的線程跟新，因此每次讀取這個(gè)域的時(shí)候都需要重新計(jì)算，而不是使用寄存器中的值，這個(gè)關(guān)鍵字不會(huì)提供任何的原子操作，也不能用來(lái)修飾final類(lèi)型的變量、

?修改后代碼為：

package?com.java; import?java.awt.GridLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; ?? import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; import?javax.swing.JScrollPane; import?javax.swing.JTextArea; ?? public?class?UnSynBank?extends?JFrame{ ????public?UnSynBank(){ ????????panel.setLayout(new?GridLayout(2,?2,?3,?3)); ????????panel.add(label1); ????????panel.add(label2); ????????JScrollPane js1 =?new?JScrollPane(oneArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js1); ????????JScrollPane js2 =?new?JScrollPane(twoArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js2); ?? ????????panel2.add(panel); ????????panel2.add(statrButton); ????????setContentPane(panel2); ?? ????????statrButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????Thread demo1 =?new?Thread(new?Transfer(bank, oneArea)); ????????????????demo1.start(); ????????????????Thread demo2 =?new?Thread(new?Transfer(bank, twoArea)); ????????????????demo2.start(); ????????????} ????????}); ?? ????????setSize(300,?400); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????} ?? ????public?static?void?main(String[] args){ ????????new?UnSynBank(); ????} ?? ????private?final?Bank bank =?new?Bank(); ????JPanel panel =?new?JPanel(); ????JPanel panel2 =?new?JPanel(); ????private?final?JButton statrButton =?new?JButton("開(kāi)始存錢(qián)"); ????private?final?JLabel label1 =?new?JLabel("一號(hào)線程"); ????private?final?JLabel label2 =?new?JLabel("二號(hào)線程"); ????private?final?JTextArea oneArea =?new?JTextArea(5,?10); ????private?final?JTextArea twoArea =?new?JTextArea(5,?10); } ?? /** ?* 表示銀行的類(lèi) ?* */ class?Bank{ ????public?Bank(){ ?? ????} ?? ????public?synchronized?void?deposit(int?money){ ????????account += money; ????} ?? ????public?int?getAccount(){ ????????return?account; ????} ?? ????private?volatile?int?account =?100; } ?? /** ?* 表示往賬戶(hù)存錢(qián) ?* */ class?Transfer?implements?Runnable{ ????public?Transfer(){ ?? ????} ?? ????public?Transfer(Bank bank, JTextArea textArea){ ????????this.bank = bank; ????????this.textArea = textArea; ????} ?? ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?20; ++i){ ????????????bank.deposit(10); ????????????String str = textArea.getText(); ????????????textArea.setText(str +?"賬戶(hù)余額為："?+ bank.getAccount() +?"\n"); ????????} ????} ?? ????private?Bank bank =?null; ????private?JTextArea textArea =?null; }

提醒一下：關(guān)于安全域的并發(fā)訪問(wèn)：

多線程中的非同步問(wèn)題出現(xiàn)在對(duì)于域的讀寫(xiě)上的時(shí)候，如果讓域自身避免這個(gè)問(wèn)題的話，則不需要修改操作的方法，在java中有3中域自身就可以避免非同步問(wèn)題：final域，使用volatile域，以及有鎖保護(hù)的域。

使用重入鎖實(shí)現(xiàn)線程同步

1 2	import?java.util.concurrent.locks.Lock; import?java.util.concurrent.locks.ReentrantLock;

可以在程序中添加上面兩行代碼，。然后將Bank修改為：

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class?Bank{ ????public?Bank(){ ????} ????public?void?deposit(int?money){ ????????lock.lock(); ????????try{ ????????????account += money; ????????}finally{ ????????????lock.unlock(); ????????} ????} ????public?int?getAccount(){ ????????return?account; ????} ????private?final?Lock lock =?new?ReentrantLock(); ????private?int?account =?100; }

這樣也可以解決非同步問(wèn)題。至于這個(gè)類(lèi)，大家可以自行去查看API，我只是在這里提醒一下，如果synchronized能夠滿(mǎn)足需求的話，就使用synchronized關(guān)鍵字，因?yàn)檫@個(gè)可以簡(jiǎn)化代碼，如果需要更加高級(jí)的功能的時(shí)候，就使用Lock對(duì)象，在使用ReentrantLock的時(shí)候，一定要注意及時(shí)釋放鎖，否則程序會(huì)出現(xiàn)死鎖。

使用線程局部變量實(shí)現(xiàn)線程同步

這個(gè)例子演示的是兩個(gè)線程同時(shí)修改一個(gè)變量，運(yùn)行結(jié)果：

可以發(fā)現(xiàn)，每個(gè)線程完成修改之后的副本是完全獨(dú)立的，如果使用TreadLocal來(lái)管理變量，則每個(gè)使用這個(gè)變量的線程都會(huì)獲得這個(gè)變量的一個(gè)副本。，并且可以隨意修改這個(gè)副本，每個(gè)線程之間不會(huì)影響。

TreadLocal和同步機(jī)制都是為了解決多線程中的相同變量訪問(wèn)沖突的問(wèn)題的，前者采用的是空間還時(shí)間，后者采用的是時(shí)間換空間

代碼如下：

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class?Bank{ ????public?Bank(){ ????} ????public?void?deposit(int?money){ ????????account.set(account.get() + money); ????} ????public?int?getAccount(){ ????????return?account.get(); ????} ????private?static?ThreadLocal<Integer> account =?new?ThreadLocal<Integer>(){ ????????@Override ????????protected?Integer initialValue(){ ????????????return?100; ????????} ????}; }

線程之間的通信

還記得我在我的筆記java IO總結(jié)中給出了一個(gè)使用管道流進(jìn)行線程之間通信的例子：

package?Thread; import?java.io.IOException; import?java.io.PipedInputStream; import?java.io.PipedOutputStream; /** ?* 使用管道流進(jìn)行線程之間的通信 ?* */ public?class?PipedTreadDemo{ ????public?static?void?main(String[] args){ ????????Sender send =?new?Sender(); ????????Reciver rec =?new?Reciver(); ????????try{ ????????????send.getOut().connect(rec.getReciver()); ????????}catch(Exception e){ ????????????e.printStackTrace(); ????????} ????????new?Thread(send).start(); ????????new?Thread(rec).start(); ????} } /** ?* 消息發(fā)送類(lèi) ?* */ class?Sender?implements?Runnable{ ????private?PipedOutputStream out =?null; ????public?Sender(){ ????????out =?new?PipedOutputStream(); ????} ????public?PipedOutputStream getOut(){ ????????return?this.out; ????} ????@Override ????public?void?run(){ ????????String str =?"rollen holt"; ????????try{ ????????????out.write(str.getBytes()); ????????}catch(IOException e){ ????????????e.printStackTrace(); ????????} ????????try{ ????????????out.close(); ????????}catch(IOException e){ ????????????e.printStackTrace(); ????????} ????} } /** ?* 消息接受類(lèi) ?* */ class?Reciver?implements?Runnable{ ????private?PipedInputStream input =?null; ????public?Reciver(){ ????????input =?new?PipedInputStream(); ????} ????public?PipedInputStream getReciver(){ ????????return?this.input; ????} ????@Override ????public?void?run(){ ????????byte[] bytes =?new?byte[1024]; ????????int?len =?0; ????????try{ ????????????len = input.read(bytes); ????????}catch(IOException e){ ????????????e.printStackTrace(); ????????} ????????try{ ????????????input.close(); ????????}catch(IOException e){ ????????????e.printStackTrace(); ????????} ????????System.out.println("讀取的內(nèi)容為："?+?new?String(bytes,?0, len)); ????} }

【運(yùn)行結(jié)果】：

讀取的內(nèi)容為：rollen holt

下面，我們?cè)谕降那疤嵯?#xff0c;在舉出一個(gè)線程通信的例子：

首先擺出運(yùn)行結(jié)果再說(shuō)：

程序代碼如下：

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package?Thread; /** ?* 線程之間的通信 ?* */ import?java.awt.GridLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; import?javax.swing.JScrollPane; import?javax.swing.JTextArea; public?class?TreadCommunicate?extends?JFrame{ ????public?TreadCommunicate(){ ????????panel.setLayout(new?GridLayout(2,?2,?3,?3)); ????????panel.add(label1); ????????panel.add(label2); ????????JScrollPane js1 =?new?JScrollPane(oneArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js1); ????????JScrollPane js2 =?new?JScrollPane(twoArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js2); ????????statrButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????Sender sender =?new?Sender(); ????????????????Thread demo1 =?new?Thread(sender); ????????????????Thread demo2 =?new?Thread(new?Receiver(sender)); ????????????????demo1.start(); ????????????????demo2.start(); ????????????} ????????}); ????????panel2.add(panel); ????????panel2.add(statrButton); ????????setContentPane(panel2); ????????setSize(300,?400); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????} ????public?static?void?main(String[] args){ ????????new?TreadCommunicate(); ????} ????/** ?????* 賣(mài)家 ?????* */ ????class?Sender?implements?Runnable{ ????????@Override ????????public?void?run(){ ????????????for(int?i =?0; i <?5; ++i){ ????????????????// 如果已經(jīng)發(fā)送，那么就等待 ????????????????while(isValid){ ????????????????????Thread.yield(); ????????????????} ????????????????product = products[i]; ????????????????String text = oneArea.getText(); ????????????????oneArea.setText(text +?"發(fā)送"?+ product +?"\n"); ????????????????try{ ????????????????????Thread.sleep(1000); ????????????????}catch(Exception e){ ????????????????????e.printStackTrace(); ????????????????} ????????????????isValid =?true; ????????????} ????????} ????????public?boolean?isisValid(){ ????????????return?this.isValid; ????????} ????????public?void?setValid(boolean?flag){ ????????????this.isValid = flag; ????????} ????????public?String getProduct(){ ????????????return?product; ????????} ????????private?volatile?String[] products = {?"《金瓶梅》",?"《紅樓夢(mèng)》",?"《平凡的世界》", ????????????????"《流氓老師》",?"《西游記》"?}; ????????private?volatile?boolean?isValid =?false; ????????private?volatile?String product; ????}// end sender ????/** ?????* 買(mǎi)家 ?????* */ ????class?Receiver?implements?Runnable{ ????????public?Receiver(){ ????????} ????????public?Receiver(Sender sender){ ????????????this.sender = sender; ????????} ????????@Override ????????public?void?run(){ ????????????for(int?i =?0; i <?5; ++i){ ????????????????// 如果沒(méi)有發(fā)送，就等待 ????????????????while(!sender.isisValid()){ ????????????????????Thread.yield(); ????????????????} ????????????????String test = twoArea.getText(); ????????????????twoArea.setText(test +?"接受到"?+ sender.getProduct() +?"\n"); ????????????????try{ ????????????????????Thread.sleep(1000); ????????????????}catch(Exception e){ ????????????????????e.printStackTrace(); ????????????????} ????????????????sender.setValid(false); ????????????} ????????} ????????private?Sender sender; ????} ????JPanel panel =?new?JPanel(); ????JPanel panel2 =?new?JPanel(); ????private?final?JButton statrButton =?new?JButton("開(kāi)始交易"); ????private?final?JLabel label1 =?new?JLabel("賣(mài)家"); ????private?final?JLabel label2 =?new?JLabel("買(mǎi)家"); ????private?final?JTextArea oneArea =?new?JTextArea(5,?10); ????private?final?JTextArea twoArea =?new?JTextArea(5,?10); }

死鎖的范例

下面絕對(duì)不是本人蛋疼的寫(xiě)出這個(gè)一個(gè)更加叫人蛋疼的程序。只是給出了一個(gè)例子：

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/** ?* 簡(jiǎn)單的死鎖 ?* */ public?class?DeadLockDemo?implements?Runnable{ ????@Override ????public?void?run(){ ????????// 獲得當(dāng)前線程的名字 ????????String str = Thread.currentThread().getName(); ????????System.out.println(str +?": flag= "?+ flag); ????????if(flag){ ????????????synchronized?(obj1){ ????????????????try{ ????????????????????Thread.sleep(1000); ????????????????}catch(Exception e){ ????????????????????e.printStackTrace(); ????????????????} ????????????????System.out.println(str +?"已經(jīng)進(jìn)入同步快obj1，準(zhǔn)備進(jìn)入同步快obj2"); ????????????????synchronized?(obj2){ ????????????????????System.out.println(str +?"已經(jīng)進(jìn)入同步快obj2"); ????????????????} ????????????} ????????} ????????if(!flag){ ????????????synchronized?(obj2){ ????????????????try{ ????????????????????Thread.sleep(1000); ????????????????}catch(Exception e){ ????????????????????e.printStackTrace(); ????????????????} ????????????????System.out.println(str +?"已經(jīng)進(jìn)入同步快obj2，準(zhǔn)備進(jìn)入同步快obj1"); ????????????????synchronized?(obj1){ ????????????????????System.out.println(str +?"已經(jīng)進(jìn)入同步快obj1"); ????????????????} ????????????} ????????} ????} ????public?static?void?main(String[] args){ ????????DeadLockDemo demo1 =?new?DeadLockDemo(); ????????DeadLockDemo demo2 =?new?DeadLockDemo(); ????????demo1.flag =?true; ????????demo2.flag =?false; ????????new?Thread(demo1).start(); ????????new?Thread(demo2).start(); ????} ????private?boolean?flag; ????private?final?Object obj1 =?new?Object(); ????private?final?Object obj2 =?new?Object(); }

【運(yùn)行結(jié)果】

（我承認(rèn)我今天RP爆發(fā)，我運(yùn)行了10次，還是沒(méi)出現(xiàn)死鎖那種情況，但是這個(gè)程序確實(shí)可以產(chǎn)生死鎖的，哪位運(yùn)行這個(gè)程序，要是產(chǎn)生了死鎖，麻煩說(shuō)一下，謝謝）

使用線程池優(yōu)化多線程編程

這個(gè)例子使用的是Executors類(lèi)，讀者自行查看API，因?yàn)橐庹f(shuō)的話，就太多了。

下面這個(gè)例子給出了使用線程池和不使用線程池的情況下的效率的問(wèn)題。

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45

package?Thread; import?java.util.concurrent.ExecutorService; import?java.util.concurrent.Executors; /** ?* 使用線程池優(yōu)化多線程編程 ?* */ public?class?ThreadPoolDemo{ ????public?static?void?main(String[] args){ ????????Runtime run = Runtime.getRuntime(); ????????// 為了減少誤差 ????????run.gc(); ????????long?currentTime = System.currentTimeMillis(); ????????long?freemonery = run.freeMemory(); ????????for(int?i =?0; i <?10000; ++i){ ????????????new?Thread(new?Temo()).start(); ????????} ????????System.out.println("獨(dú)立運(yùn)行10000個(gè)線程占用內(nèi)存為：" ????????????????+ (freemonery - run.freeMemory())); ????????System.out.println("獨(dú)立運(yùn)行10000個(gè)線程占用時(shí)間為：" ????????????????+ (System.currentTimeMillis() - currentTime)); ????????// 下面使用線程池來(lái)試試 ????????run.gc(); ????????freemonery = run.freeMemory(); ????????currentTime = System.currentTimeMillis(); ????????ExecutorService executorService = Executors.newFixedThreadPool(3); ????????for(int?i =?0; i <?10000; ++i){ ????????????executorService.submit(new?Temo()); ????????} ????????System.out.println("使用線程池運(yùn)行10000個(gè)線程占用內(nèi)存為：" ????????????????+ (freemonery - run.freeMemory())); ????????System.out.println("使用線程池運(yùn)行10000個(gè)線程占用時(shí)間為：" ????????????????+ (System.currentTimeMillis() - currentTime)); ????} } class?Temo?implements?Runnable{ ????@Override ????public?void?run(){ ????????count++; ????} ????private?int?count =?0; }

【運(yùn)行結(jié)果】：

獨(dú)立運(yùn)行10000個(gè)線程占用內(nèi)存為：3490440

獨(dú)立運(yùn)行10000個(gè)線程占用時(shí)間為：1808

使用線程池運(yùn)行10000個(gè)線程占用內(nèi)存為：1237424

使用線程池運(yùn)行10000個(gè)線程占用時(shí)間為：62

關(guān)于哲學(xué)家就餐的問(wèn)題

由于代碼比較長(zhǎng)，所以單獨(dú)列出為一篇文章

地址：http://www.cnblogs.com/rollenholt/archive/2011/09/15/2178004.html

使用信號(hào)量實(shí)現(xiàn)線程同步

現(xiàn)在我們繼續(xù)回答之前銀行存款的問(wèn)題，相信大家還沒(méi)有忘記，哈哈，真是不好意思，本來(lái)線程同步這一塊應(yīng)該整理在一起的。

一個(gè)信號(hào)量有3中操作，而且他們?nèi)慷际窃拥?#xff0c;初始化，增加，減少。增加可以為一個(gè)進(jìn)程解除阻塞，減少可以為一個(gè)進(jìn)程進(jìn)入阻塞。

Semaphore類(lèi)是一個(gè)技術(shù)信號(hào)量，從概念上信號(hào)量維持了一個(gè)許可集。

現(xiàn)在我們繼續(xù)看上面的銀行存款問(wèn)題：

package?Thread; import?java.awt.GridLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; import?java.util.concurrent.Semaphore; import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; import?javax.swing.JScrollPane; import?javax.swing.JTextArea; public?class?synDemo?extends?JFrame{ ????public?synDemo(){ ????????panel.setLayout(new?GridLayout(2,?2,?3,?3)); ????????panel.add(label1); ????????panel.add(label2); ????????JScrollPane js1 =?new?JScrollPane(oneArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js1); ????????JScrollPane js2 =?new?JScrollPane(twoArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js2); ????????panel2.add(panel); ????????panel2.add(statrButton); ????????setContentPane(panel2); ????????statrButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????Thread demo1 =?new?Thread(new?Transfer1(bank, oneArea, ????????????????????????semaphore)); ????????????????demo1.start(); ????????????????Thread demo2 =?new?Thread(new?Transfer1(bank, twoArea, ????????????????????????semaphore)); ????????????????demo2.start(); ????????????} ????????}); ????????setSize(300,?400); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????} ????public?static?void?main(String[] args){ ????????new?synDemo(); ????} ????Semaphore semaphore =?new?Semaphore(1,?true); ????private?final?Bank1 bank =?new?Bank1(); ????JPanel panel =?new?JPanel(); ????JPanel panel2 =?new?JPanel(); ????private?final?JButton statrButton =?new?JButton("開(kāi)始存錢(qián)"); ????private?final?JLabel label1 =?new?JLabel("一號(hào)線程"); ????private?final?JLabel label2 =?new?JLabel("二號(hào)線程"); ????private?final?JTextArea oneArea =?new?JTextArea(5,?10); ????private?final?JTextArea twoArea =?new?JTextArea(5,?10); } /** ?* 表示銀行的類(lèi) ?* */ class?Bank1{ ????public?Bank1(){ ????} ????public?void?deposit(int?money){ ????????account += money; ????} ????public?int?getAccount(){ ????????return?account; ????} ????private?int?account; } /** ?* 表示往賬戶(hù)存錢(qián) ?* */ class?Transfer1?implements?Runnable{ ????public?Transfer1(){ ????} ????public?Transfer1(Bank1 bank, JTextArea textArea, Semaphore semaphore){ ????????this.bank = bank; ????????this.textArea = textArea; ????????this.semaphore = semaphore; ????} ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?20; ++i){ ????????????// 獲得許可 ????????????try{ ????????????????semaphore.acquire(); ????????????}catch(InterruptedException e){ ????????????????e.printStackTrace(); ????????????} ????????????bank.deposit(10); ????????????String str = textArea.getText(); ????????????textArea.setText(str +?"賬戶(hù)余額為："?+ bank.getAccount() +?"\n"); ????????????// 釋放許可 ????????????semaphore.release(); ????????} ????} ????// 注意 ????private?Semaphore semaphore; ????private?Bank1 bank =?null; ????private?JTextArea textArea =?null; }

運(yùn)行結(jié)果：

使用原子變量實(shí)現(xiàn)線程同步

package?Thread; import?java.awt.GridLayout; import?java.awt.event.ActionEvent; import?java.awt.event.ActionListener; import?java.util.concurrent.atomic.AtomicInteger; import?javax.swing.JButton; import?javax.swing.JFrame; import?javax.swing.JLabel; import?javax.swing.JPanel; import?javax.swing.JScrollPane; import?javax.swing.JTextArea; public?class?synDemo?extends?JFrame{ ????public?synDemo(){ ????????panel.setLayout(new?GridLayout(2,?2,?3,?3)); ????????panel.add(label1); ????????panel.add(label2); ????????JScrollPane js1 =?new?JScrollPane(oneArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js1); ????????JScrollPane js2 =?new?JScrollPane(twoArea, ????????????????JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, ????????????????JScrollPane.HORIZONTAL_SCROLLBAR_ALWAYS); ????????panel.add(js2); ????????panel2.add(panel); ????????panel2.add(statrButton); ????????setContentPane(panel2); ????????statrButton.addActionListener(new?ActionListener(){ ????????????@Override ????????????public?void?actionPerformed(ActionEvent e){ ????????????????Thread demo1 =?new?Thread(new?Transfer1(bank, oneArea)); ????????????????demo1.start(); ????????????????Thread demo2 =?new?Thread(new?Transfer1(bank, twoArea)); ????????????????demo2.start(); ????????????} ????????}); ????????setSize(300,?400); ????????setVisible(true); ????????setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ????} ????public?static?void?main(String[] args){ ????????new?synDemo(); ????} ????private?final?Bank1 bank =?new?Bank1(); ????JPanel panel =?new?JPanel(); ????JPanel panel2 =?new?JPanel(); ????private?final?JButton statrButton =?new?JButton("開(kāi)始存錢(qián)"); ????private?final?JLabel label1 =?new?JLabel("一號(hào)線程"); ????private?final?JLabel label2 =?new?JLabel("二號(hào)線程"); ????private?final?JTextArea oneArea =?new?JTextArea(5,?10); ????private?final?JTextArea twoArea =?new?JTextArea(5,?10); } /** ?* 表示銀行的類(lèi) ?* */ class?Bank1{ ????public?Bank1(){ ????} ????public?void?deposit(int?money){ ????????account.addAndGet(money); ????} ????public?int?getAccount(){ ????????return?account.get(); ????} ????//注意 ????private?final?AtomicInteger account =?new?AtomicInteger(100); } /** ?* 表示往賬戶(hù)存錢(qián) ?* */ class?Transfer1?implements?Runnable{ ????public?Transfer1(){ ????} ????public?Transfer1(Bank1 bank, JTextArea textArea){ ????????this.bank = bank; ????????this.textArea = textArea; ????} ????@Override ????public?void?run(){ ????????for(int?i =?0; i <?20; ++i){ ????????????bank.deposit(10); ????????????String str = textArea.getText(); ????????????textArea.setText(str +?"賬戶(hù)余額為："?+ bank.getAccount() +?"\n"); ????????} ????} ????private?Bank1 bank =?null; ????private?JTextArea textArea =?null; }

【運(yùn)行結(jié)果】：

總結(jié)

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