對同一個對象進(jìn)行多線程操作時，如何保證線程執(zhí)行結(jié)果的一致性？我們需要對線程操作對象加同步鎖。（這是一道面試題）
需求描述
1-20個數(shù)字
a線程打印奇數(shù)：1，3，5，7，9，11，13，15，17，19
b線程打印偶數(shù)：2，4，6，8，10，12，14，16，18，20
c線程在ab兩個線程執(zhí)行完了之后打印結(jié)果：“success”。
線程代碼實現(xiàn)
num.java
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package com.boonya.thread.test; /** * @classname: num * @description: todo(加鎖計算對象) * @author: pengjunlin * @motto: 學(xué)習(xí)需要毅力，那就秀毅力 * @date 2019-01-14 22:47 */public class num { int value=1;} |
athread.java
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package com.boonya.thread.test; /*** @classname: athread* @description: todo(奇數(shù)線程)* @author: pengjunlin* @motto: 學(xué)習(xí)需要毅力，那就秀毅力* @date 2019-01-14 22:26*/public class athread implements runnable{ num num; public athread(num num){ this.num=num; } public void run() { while (num.value<20){ synchronized (num){ if(num.value%2!=0){ system.out.println("athread:"+ num.value); num.value++; } } } }} |
bthread.java
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package com.boonya.thread.test; /** * @classname: bthread * @description: todo(偶數(shù)線程) * @author: pengjunlin * @motto: 學(xué)習(xí)需要毅力，那就秀毅力 * @date 2019-01-14 22:26 */public class bthread implements runnable { num num; public bthread(num num){ this.num=num; } public void run() { while (num.value<=20){ synchronized (num){ if(num.value%2==0){ system.out.println("bthread:"+ num.value); num.value++; } } } } } |
cthread.java
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package com.boonya.thread.test; /** * @classname: cthread * @description: todo(等待結(jié)果線程) * @author: pengjunlin * @motto: 學(xué)習(xí)需要毅力，那就秀毅力 * @date 2019-01-14 22:26 */public class cthread implements runnable { num num; public cthread(num num){ this.num=num; } public void run() { while (num.value<20){ try { thread.sleep(1); } catch (interruptedexception e) { e.printstacktrace(); } } system.out.println("cthread:success!"); } } |
maintest.java
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package com.boonya.thread.test; import java.util.arraylist;import java.util.list; /** * @classname: maintest * @description: todo(線程測試) * @author: pengjunlin * @motto: 學(xué)習(xí)需要毅力，那就秀毅力 * @date 2019-01-14 21:54 */public class maintest { public static void main(string[] args) { num num=new num(); thread a=new thread(new athread(num)); thread b=new thread(new bthread(num)); thread c=new thread(new cthread(num)); a.start(); b.start(); c.start(); }} |
測試結(jié)果
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"c:\program files\java\jdk1.8.0_121\bin\java" "-javaagent:c:\users\boonya\appdata\roaming\jetbrains\intellij idea 2017.2.5\lib\idea_rt.jar=51911:c:\users\boonya\appdata\roaming\jetbrains\intellij idea 2017.2.5\bin" -dfile.encoding=utf-8 -classpath "c:\program files\java\jdk1.8.0_121\jre\lib\charsets.jar;c:\program files\java\jdk1.8.0_121\jre\lib\deploy.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\access-bridge-64.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\cldrdata.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\dnsns.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\jaccess.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\jfxrt.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\localedata.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\nashorn.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\sunec.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\sunjce_provider.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\sunmscapi.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\sunpkcs11.jar;c:\program files\java\jdk1.8.0_121\jre\lib\ext\zipfs.jar;c:\program files\java\jdk1.8.0_121\jre\lib\javaws.jar;c:\program files\java\jdk1.8.0_121\jre\lib\jce.jar;c:\program files\java\jdk1.8.0_121\jre\lib\jfr.jar;c:\program files\java\jdk1.8.0_121\jre\lib\jfxswt.jar;c:\program files\java\jdk1.8.0_121\jre\lib\jsse.jar;c:\program files\java\jdk1.8.0_121\jre\lib\management-agent.jar;c:\program files\java\jdk1.8.0_121\jre\lib\plugin.jar;c:\program files\java\jdk1.8.0_121\jre\lib\resources.jar;c:\program files\java\jdk1.8.0_121\jre\lib\rt.jar;c:\users\boonya\desktop\javaalgorithm\target\test-classes;c:\users\boonya\desktop\javaalgorithm\target\classes" com.boonya.thread.test.maintestathread:1bthread:2athread:3bthread:4athread:5bthread:6athread:7bthread:8athread:9bthread:10athread:11bthread:12athread:13bthread:14athread:15bthread:16athread:17bthread:18athread:19bthread:20cthread:success! process finished with exit code 0 |
注意：synchronized 作為方法塊使用時需要只能對對象加鎖，不能是常用數(shù)據(jù)類型。
ab線程改進(jìn):使用線程等待和通知
athread.java
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package com.boonya.thread.test; /*** @classname: athread* @description: todo(奇數(shù)線程)* @author: pengjunlin* @motto: 學(xué)習(xí)需要毅力，那就秀毅力* @date 2019-01-14 22:26*/public class athread implements runnable{ num num; public athread(num num){ this.num=num; } public void run() { while (num.value<20){ synchronized (num){ if(num.value%2!=0){ system.out.println("athread:"+ num.value); num.value++; //num.notify(); num.notifyall(); }else{ try { num.wait(); } catch (interruptedexception e) { e.printstacktrace(); } } } } }} |
bthread.java
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package com.boonya.thread.test; /** * @classname: bthread * @description: todo(偶數(shù)線程) * @author: pengjunlin * @motto: 學(xué)習(xí)需要毅力，那就秀毅力 * @date 2019-01-14 22:26 */public class bthread implements runnable { num num; public bthread(num num){ this.num=num; } public void run() { while (num.value<=20){ synchronized (num){ if(num.value%2==0){ system.out.println("bthread:"+ num.value); num.value++; //num.notify(); num.notifyall(); }else{ try { num.wait(); } catch (interruptedexception e) { e.printstacktrace(); } } } } } } |
注：線程等待和通知的操作是節(jié)省cpu運算的一種方式，避免cpu空轉(zhuǎn)（線程方法一直不停地跑類似于死循環(huán)是很可怕的），如果是要讓線程停下來需要調(diào)用線程的wait()。
以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持服務(wù)器之家。
原文鏈接：https://blog.csdn.net/boonya/article/details/86485504
