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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN">
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<head>
<title>OpenJava : Tutorial</title>
<meta http-equiv="Keywords" content="java, openjava, reflection">
</head>
<body bgcolor="white"
text="#000000" link="#007fff" vlink="#006fdf" alink="#ff0000">
<h2><!---------------------------------------------------------------------->
<center>
<h1><font color="Blue">OpenJava Tutorial</font></h1>
</center>
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<hr width="100%">
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7. <font color="blue">Synchronization of Translation</font>
</h2>
<p>
As the default behavior of OpenJava compiler, there is no assurance of
callee-side translation ordering. In the case that we make it sure to
translate a class <b>SubMyObject</b> after a class <b>MyObject</b>, we
can use the method <code>waitTranslation()</code> in
<b>java.lang.OJClass</b>.
<br><blockquote><pre>
public void waitTranslation(OJClass)
throws MOPException
</pre></blockquote>
At the invocation of this method, the translation on the current
class declaration stops and it return to continue after the
translation on the class given as the argument finished.
<h3>7.1. Simple Examples</h3>
<p>
Furthermore, the part where that class is used comes. There are
several part related to the use of class. i.e. object allocations,
method calls, field accesses, .. We call this kind of translation
<i>caller-side translation</i>.
<p>
For the convenience of explanation, suppose a base class
<b>MyObject</b> extended by a metaclass <b>MyClass</b>, like
following:
<br><blockquote><pre><font color=darkblue>
public class <font color=black>SubMyObject</font> instantiates <font color=black>SyncClass</font> extends <font color=black>MyObject</font>
{}
class <font color=black>MyObject</font> instantiates <font color=black>AnotherClass</font>
{}
class <font color=black>SubSubMyObject</font> instantiates <font color=black>SyncClass</font> extends <font color=black>SubMyObject</font>
{}
</font></pre></blockquote>
<br><blockquote><pre><font color=darkblue>
public class <font color=black>SyncClass</font> instantiates <font color=black>Metaclass</font> extends <font color=black>OJClass</font>
{
void translateDefinition() throws <font color=black>MOPException</font> {
<font color=black>OJClass</font> baseclazz = getSuperclass();
<font color=black>System</font>.out.println( getName() + "<i> is waiting for </i>" + base.getName() );
waitTranslation( baseclazz );
<font color=black>System</font>.out.println( getName() + "<i> finished</i>" );
}
}
</font></pre></blockquote>
We can see the following messages in running OpenJava compiler.
<br><blockquote><pre><font color=darkred>
MyObject is waiting for java.lang.Object
MyObject finished
SubSubMyObject is waiting for SubMyObject
SubMyObject is waiting for MyObject
SubMyObject finished
SubSubMyObject finished
</font></pre></blockquote>
<p>
<h3>7.2. Deadlocks</h3>
<p>
In the case of the system detects some deadlocks,
<code>waitTranslation()</code> throws an exception
<code>MOPException</code>. If already the translation of
a class <b>A</b> were waiting for the translation of a class <b>B</b>,
the invocation of <code>waitTranslation()</code> on the translation
of the class <b>B</b> would not block but throw an exception.
<p>
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<hr width="100%">
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<center>
Please send any message to :
<address>
mich@acm.org
</address><BR>
</center>
<font size=1>Copyright (C) 1999 by Michaki Tatsubori.</font><br>
<font size=1>Java(TM) is a trademark of Sun Microsystems, Inc.</font>
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