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From "Zhihong Yu (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5290) [FindBugs] Synchronization on boxed primitive
Date Mon, 30 Jan 2012 19:17:10 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5290?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13196335#comment-13196335
] 

Zhihong Yu commented on HBASE-5290:
-----------------------------------

This is not recommended:
{code}
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Calendar;
-import java.util.GregorianCalendar;
-import java.util.List;
+import java.util.*;
{code}
Imports should be specific.
                
> [FindBugs] Synchronization on boxed primitive
> ---------------------------------------------
>
>                 Key: HBASE-5290
>                 URL: https://issues.apache.org/jira/browse/HBASE-5290
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 0.94.0
>            Reporter: Liyin Tang
>            Assignee: Liyin Tang
>            Priority: Minor
>         Attachments: HBASE-5290.patch, HBASE-5290.patch
>
>
> This bug is reported by the findBugs tool, which is a static analysis tool.
> Bug: Synchronization on Integer in org.apache.hadoop.hbase.regionserver.compactions.CompactSelection.emptyFileList()
> The code synchronizes on a boxed primitive constant, such as an Integer.
> private static Integer count = 0;
> ...
>   synchronized(count) {
>      count++;
>      }
> ...
> Since Integer objects can be cached and shared, this code could be synchronizing on the
same object as other, unrelated code, leading to unresponsiveness and possible deadlock
> See CERT CON08-J. Do not synchronize on objects that may be reused for more information.
> Confidence: Normal, Rank: Troubling (14)
> Pattern: DL_SYNCHRONIZATION_ON_BOXED_PRIMITIVE 
> Type: DL, Category: MT_CORRECTNESS (Multithreaded correctness)

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