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List:       rxtx
Subject:    Re: AW: [Rxtx] singleton design pattern [and synchronization]
From:       "Dr. Douglas Lyon" <lyon () docjava ! com>
Date:       2006-01-20 8:04:09
Message-ID: p0602041dbff648d7fd78 () [192 ! 168 ! 1 ! 152]
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Hi All,
I have taken Brian's suggestion to heart:
public class SafeCommDriver {
     private static RXTXCommDriver driver = null;

     private SafeCommDriver() {
     }

     public synchronized static CommDriver getInstance() {
         if (driver == null && NativeLibDetect.isLibInPath("rxtxSerial")) {
             driver = new RXTXCommDriver();
             driver.initialize();
         }
         return driver;
     }
Does look like better code...(thanks Brian!).

I have heard of the multi-return
issue in the past and it concerns me that we have no clear resolution
on the matter. Perhaps it is too off-point for this list.
  - Doug


>>Doug has been working hard on this off the list and I hope he will 
>>share his work so far for further comments.
>
>
>I have an app that talks to VCR's using RS-422. It's multi-threaded 
>and works well with java comm 2.0 but is not so friendly with RXTX 
>(I've tried it with both 2.0 and 2.1). When Doug makes his code 
>changes available I'd be happy to take them for spin and see if I 
>run into any threading problems with it.
>
>BTW, The problems I had with RXTX were a) Not getting responses on 
>windows (I suspect this has to do with the flow control setting bug 
>that was recently reported.) b) The classpathx version of the 
>java.comm libraries installed via fink on Mac OS X have some 
>threading issues. My application throws a 
>'java.lang.IllegalMonitorStateException: current thread not owner', 
>which tells me something isn't synchronized correctly.
>
>@ Dr. Douglas Lyon
>
>>I did hear that some people don't like multiple exit points.
>
>Sorry, I wasn't make myself clear. I wasn't intending on starting a 
>debate about multiple return statements. My point was really that 
>the getInstance method is basically a lazy-initializer. So it's 
>really only doing 2 things 1) Instantiating as instance if needed 2) 
>return the instance. 3 returns seemed like a bit of overkill, that's 
>all.
>
>Cheers
>Brian Schlining
>
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