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POIs the != check thread safe?
primarykey
Id
18460580
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18460710
AnswerCount
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ClosedDate
CommentCount
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CommunityOwnedDate
CreationDate
2013-08-27T08:27:56.433
FavoriteCount
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2016-04-15T12:57:05.530
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2013-08-30T23:35:57.450
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Score
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text
Body
I know that compound operations such as <code>i++</code> are not thread safe as they involve multiple operations. But is checking the reference with itself a thread safe operation? <pre><code>a != a //is this thread-safe </code></pre> I tried to program this and use multiple threads but it didn't fail. I guess I could not simulate race on my machine. <h2>EDIT:</h2> <pre><code>public class TestThreadSafety { private Object a = new Object(); public static void main(String[] args) { final TestThreadSafety instance = new TestThreadSafety(); Thread testingReferenceThread = new Thread(new Runnable() { @Override public void run() { long countOfIterations = 0L; while(true){ boolean flag = instance.a != instance.a; if(flag) System.out.println(countOfIterations + ":" + flag); countOfIterations++; } } }); Thread updatingReferenceThread = new Thread(new Runnable() { @Override public void run() { while(true){ instance.a = new Object(); } } }); testingReferenceThread.start(); updatingReferenceThread.start(); } } </code></pre> This is the program that I am using to test the thread-safety. <h2>Weird behavior</h2> As my program starts between some iterations I get the output flag value, which means that the reference <code>!=</code> check fails on the same reference. BUT after some iterations the output becomes constant value <code>false</code> and then executing the program for a long long time does not generate a single <code>true</code> output. As the output suggests after some n (not fixed) iterations the output seems to be constant value and does not change. Output: For some iterations: <pre><code>1494:true 1495:true 1496:true 19970:true 19972:true 19974:true //after this there is not a single instance when the condition becomes true </code></pre>
Tags
<java><multithreading><thread-safety><atomic><race-condition>
Title
Is the != check thread safe?
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1. PO
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 PTAnswer
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1. This table or related slice is empty.
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1. PTQuestion
UserLastEditorUserId
1. USNarendra Pathai
UserOwnerUserId
1. USNarendra Pathai
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1. PO
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2. PO
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