Re: Findbugs and locks?

From:
Knute Johnson <nospam@rabbitbrush.frazmtn.com>
Newsgroups:
comp.lang.java.help
Date:
Wed, 30 Jul 2008 12:33:19 -0700
Message-ID:
<4890c1fe$0$4010$b9f67a60@news.newsdemon.com>
Jeff Higgins wrote:

Sorry for the confusion, I too quickly posted an experimental version.
I can't figure out what exception path the following might close, but
FindBugs does not produce a bug report for the following:

import java.io.IOException;
import java.util.concurrent.locks.ReentrantReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock.WriteLock;

public class SSCCE {

  static ReentrantReadWriteLock lockArray[];
  static {
    lockArray =
      new ReentrantReadWriteLock[5];
    for (int i=0; i<lockArray.length; i++)
      lockArray[i] = new ReentrantReadWriteLock();
  }

  static void method(int n) throws IOException {

    WriteLock lock = lockArray[n].writeLock();
    lock.lock();
    try {
      // do some disk I/O
    } finally {
      lock.unlock();
    }
  }

  public static void main(String[] args) {}
}


Ah but look at what does!

   static void method(int n) throws IOException {

// WriteLock lock = lockArray[n].writeLock();
// lock.lock();
       lockArray[n].writeLock().lock();
     try {
       // do some disk I/O
     } finally {
// lock.unlock();
         lockArray[n].writeLock().unlock();
     }
   }

I think it is a bug in findbugs. I think I'll drop them a line.

Thanks,

--

Knute Johnson
email s/nospam/knute2008/

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