I discovered that using synchronized blocks in code compiled w/ SDK1.4 compiler generates byte code that won't run under JDK1.2. Specifically, 1.2 VM throws a java.lang.IllegalMonitorStateException and terminates execution of my program when it encounters a synchronized code block. . . YIKES!

Has anyone has had similar experience(s)? (Please post here) This is a real problem for my company since our products need to be binary compatibile back to JDK 1.2.x.

Chris
San Mateo, CA

PS -- I submitted this apparent bug to Sun yesterday.

========================
MY ENVIRONMENT
**1.4 environment** (compile code w/ javac.exe)
C:\jdk1.4.0\bin\java -version
java version "1.4.0-beta3"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.0-beta3-b84)
Java HotSpot(TM) Client VM (build 1.4.0-beta3-b84, mixed mode)

**1.2 environment** (execute bytecode w/ java.exe)
C:\jdk1.2.2\bin\java -version
java version "1.2.2"
Classic VM (build JDK-1.2.2-W, native threads, symcjit)

========================
You can reproduce the behavior by compiling the code in Merlin's javac:

C:\jdk1.4.0\bin>javac C:\Test\TestSynchronizedBlock.java

and running the bytecode in JDK1.2:

C:\Test>C:\jdk1.2.2\bin\java TestSynchronizedBlock

Example source code:

============== BEGIN CODE ==============
public class TestSynchronizedBlock
{
 
  public TestSynchronizedBlock()
  {
    super();
    
    synchronized(this)
    {
      System.out.println("Hello World!");
    }
  }
  
  public static void main(java.lang.String[] args)
  {
    TestSynchronizedBlock test = new TestSynchronizedBlock();
  }
  }
============== END OF CODE ==============

Will result in output like this:

Hello World!
Exception in thread "main" java.lang.IllegalMonitorStateException: current thread not owner
        at TestSynchronizedBlock.main(TestSynchronizedBlock.java:16)

Workaround: You can use a static method instead, which seems to run ok -- try something like this:

============== BEGIN CODE ==============
public class TestSynchronizedBlock2
{
 
  public TestSynchronizedBlock2()
  {
    super();
    
    //synchronized(this)
    {
      // call synchronized method instead
      SynchronizedMethod();
    }
  }
 
  synchronized void SynchronizedMethod()
  {
    System.out.println("Hello World!");
  }
  
  public static void main(java.lang.String[] args)
  {
    TestSynchronizedBlock2 test = new TestSynchronizedBlock2();
  }
  }
============== END OF CODE ==============

 

 

This works for me when I use the Symantec Java 1.2 runtime:
java version "1.2.2.Symc"
Classic VM (build 1.2.2.Symc, native threads, symantec gc, symcjit)

I don't have the 1.2.2 JDK installed, so I cannot verify it.

Did you try using -target 1.1 on the compiler?

Chuck

 

 

Hmmm... is there a specific reason that you should use -target 1.1 in order for the bytecode to be compatible with JRE 1.2? It seems to be you'd want to use -target 1.2.

Information about the -target option to javac is in the documentation for that command: Go to http://java.sun.com/docs/ then click on J2SDK 1.4 documentation, Tool Docs, javac.