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<head>
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<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
<title>Javac Task</title>
</head>

<body>

<h2><a name="javac">Javac</a></h2>
<h3>Description</h3>
<p>Compiles a Java source tree.</p>
<p>The source and destination directory will be recursively scanned for Java
source files to compile. Only Java files that have no corresponding
<code>.class</code> file
or where the class file is older than the
<code>.java</code> file will be compiled.</p>
<p>Note: Ant uses only the names of the source and class files to find
the classes that need a rebuild. It will not scan the source and therefore
will have no knowledge about nested classes, classes that are named different
from the source file, and so on. See the
<a href="../OptionalTasks/depend.html"><code>&lt;depend&gt;</code></a> task
for dependency checking based on other than just
existence/modification times.</p>
<p>When the source files are part of a package, the directory structure of
the source tree should follow the package
hierarchy.</p>
<p>It is possible to refine the set of files that are being compiled.
This can be done with the <code>includes</code>, <code>includesfile</code>,
<code>excludes</code>, and <code>excludesfile</code>
attributes. With the <code>includes</code> or
<code>includesfile</code> attribute, you specify the files you want to
have included.
The <code>exclude</code> or <code>excludesfile</code> attribute is used
to specify
the files you want to have excluded. In both cases, the list of files
can be specified by either the filename, relative to the directory(s) specified
in the <code>srcdir</code> attribute or nested <code>&lt;src&gt;</code>
element(s), or by using wildcard patterns. See the section on
<a href="../dirtasks.html#directorybasedtasks">directory-based tasks</a>,
for information on how the
inclusion/exclusion of files works, and how to write wildcard patterns.</p>
<p>It is possible to use different compilers. This can be specified by
either setting the global <code>build.compiler</code> property, which will
affect all <code>&lt;javac&gt;</code> tasks throughout the build, or by
setting the <code>compiler</code> attribute, specific to the current
<code>&lt;javac&gt;</code> task.
<a name="compilervalues">Valid values for either the
<code>build.compiler</code> property or the <code>compiler</code>
attribute are:</a></p>
<ul>
  <li><code>classic</code> (the standard compiler of JDK 1.1/1.2) &ndash;
      <code>javac1.1</code> and
      <code>javac1.2</code> can be used as aliases.</li>
  <li><code>modern</code> (the standard compiler of JDK 1.3/1.4/1.5/1.6) &ndash;
      <code>javac1.3</code> and
      <code>javac1.4</code> and
      <code>javac1.5</code> and
      <code>javac1.6</code> can be used as aliases.</li>
  <li><code>jikes</code> (the <a
    href="http://jikes.sourceforge.net/" target="_top">Jikes</a>
    compiler).</li>
  <li><code>jvc</code> (the Command-Line Compiler from Microsoft's SDK
      for Java / Visual J++) &ndash; <code>microsoft</code> can be used
      as an alias.</li>
  <li><code>kjc</code> (the <a href="http://www.dms.at/kopi/" target="_top">kopi</a>
    compiler).</li>
  <li><code>gcj</code> (the gcj compiler from gcc).</li>
  <li><code>sj</code> (Symantec java compiler) &ndash;
      <code>symantec</code> can be used as an alias.</li>
  <li><code>extJavac</code> (run either modern or classic in a JVM of
      its own).</li>
</ul>
<p>The default is <code>javac1.x</code> with <code>x</code> depending
on the JDK version you use while you are running Ant.
If you wish to use a different compiler interface than those
supplied, you can write a class that implements the CompilerAdapter interface
(<code>package org.apache.tools.ant.taskdefs.compilers</code>). Supply the full
classname in the <code>build.compiler</code> property or the
<code>compiler</code> attribute.
</p>
<p>The fork attribute overrides the <code>build.compiler</code> property
or <code>compiler</code> attribute setting and
expects a JDK1.1 or higher to be set in <code>JAVA_HOME</code>.
</p>
<p>You can also use the <code>compiler</code> attribute to tell Ant
which JDK version it shall assume when it puts together the command
line switches - even if you set <code>fork=&quot;true&quot;</code>.
This is useful if you want to run the compiler of JDK 1.1 while you
current JDK is 1.2+.  If you use
<code>compiler=&quot;javac1.1&quot;</code> and (for example)
<code>depend=&quot;true&quot;</code> Ant will use the command line
switch <code>-depend</code> instead of <code>-Xdepend</code>.</p>
<p>This task will drop all entries that point to non-existent
files/directories from the classpath it passes to the compiler.</p>
<p>The working directory for a forked executable (if any) is the
  project's base directory.</p>
<p><strong>Windows Note:</strong>When the modern compiler is used
in unforked mode on Windows, it locks up the files present in the
classpath of the <code>&lt;javac&gt;</code> task, and does not release them.
The side effect of this is that you will not be able to delete or move
those files later on in the build.  The workaround is to fork when
invoking the compiler.</p>
<h3>Parameters</h3>
<table border="1" cellpadding="2" cellspacing="0">
  <tr>
    <td valign="top"><b>Attribute</b></td>
    <td valign="top"><b>Description</b></td>
    <td align="center" valign="top"><b>Required</b></td>
  </tr>
  <tr>
    <td valign="top">srcdir</td>
    <td valign="top">Location of the java files. (See the
     <a href="#srcdirnote">note</a> below.)</td>
    <td align="center" valign="top">Yes, unless nested <code>&lt;src&gt;</code> elements are present.</td>
  </tr>
  <tr>
    <td valign="top">destdir</td>
    <td valign="top">Location to store the class files.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">includes</td>
    <td valign="top">Comma- or space-separated list of files (may be specified using
      wildcard patterns) that must be
      included; all <code>.java</code> files are included when omitted.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">includesfile</td>
    <td valign="top">The name of a file that contains a list of files to
      include (may be specified using wildcard patterns).</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">excludes</td>
    <td valign="top">Comma- or space-separated list of files (may be specified using
      wildcard patterns) that must be excluded; no files (except default
      excludes) are excluded when omitted.</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">excludesfile</td>
    <td valign="top">The name of a file that contains a list of files to
      exclude (may be specified using wildcard patterns).</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">classpath</td>
    <td valign="top">The classpath to use.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">sourcepath</td>
    <td valign="top">The sourcepath to use; defaults to the value of the srcdir attribute (or nested <code>&lt;src&gt;</code> elements).
        To suppress the sourcepath switch, use <code>sourcepath=&quot;&quot;</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">bootclasspath</td>
    <td valign="top">
      Location of bootstrap class files. (See <a href="#bootstrap">below</a>
      for using the -X and -J-X parameters for specifing
      the bootstrap classpath).
    </td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">classpathref</td>
    <td valign="top">The classpath to use, given as a
      <a href="../using.html#references">reference</a> to a path defined elsewhere.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">sourcepathref</td>
    <td valign="top">The sourcepath to use, given as a
      <a href="../using.html#references">reference</a> to a path defined elsewhere.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">bootclasspathref</td>
    <td valign="top">Location of bootstrap class files, given as a
      <a href="../using.html#references">reference</a> to a path defined elsewhere.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">extdirs</td>
    <td valign="top">Location of installed extensions.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">encoding</td>
    <td valign="top">Encoding of source files. (Note: gcj doesn't support
      this option yet.)</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">nowarn</td>
    <td valign="top">Indicates whether the <code>-nowarn</code> switch
      should be passed to the compiler; defaults to <code>off</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">debug</td>
    <td valign="top">Indicates whether source should be compiled with
    debug information; defaults to <code>off</code>.  If set to
    <code>off</code>, <code>-g:none</code> will be passed on the
    command line for compilers that support it (for other compilers, no
    command line argument will be used).  If set to <code>true</code>,
    the value of the <code>debuglevel</code> attribute determines the
    command line argument.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">debuglevel</td>
    <td valign="top">Keyword list to be appended to the <code>-g</code>
      command-line switch.  This will be ignored by all implementations except
      <code>modern</code>, <code>classic(ver &gt;= 1.2)</code> and <code>jikes</code>.
      Legal values are <code>none</code> or a comma-separated list of the
      following keywords:
      <code>lines</code>, <code>vars</code>, and <code>source</code>.
      If <code>debuglevel</code> is not specified, by default,
      nothing will be
      appended to <code>-g</code>.  If <code>debug</code> is not turned on,
      this attribute will be ignored.
    </td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">optimize</td>
    <td valign="top">
      Indicates whether source should be compiled with
      optimization; defaults to <code>off</code>. <strong>Note</strong>
      that this flag is just ignored by Sun's <code>javac</code> starting
      with JDK 1.3 (since compile-time optimization is unnecessary).
    </td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">deprecation</td>
    <td valign="top">Indicates whether source should be compiled with
      deprecation information; defaults to <code>off</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">target</td>
    <td valign="top">Generate class files for specific VM version
    (e.g., <code>1.1</code> or <code>1.2</code>). <b>Note that the
    default value depends on the JVM that is running Ant.  In
    particular, if you use JDK 1.4+ the generated classes will not be
    usable for a 1.1 Java VM unless you explicitly set this attribute
    to the value 1.1 (which is the default value for JDK 1.1 to
    1.3).  We highly recommend to always specify this
    attribute.</b><br>
    A default value for this attribute can be provided using the magic
    <a
    href="../javacprops.html#target"><code>ant.build.javac.target</code></a>
    property.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">verbose</td>
    <td valign="top">Asks the compiler for verbose output; defaults to
      <code>no</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">depend</td> <td valign="top">Enables dependency-tracking
      for compilers that support this (<code>jikes</code> and
      <code>classic</code>).</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">includeAntRuntime</td>
    <td valign="top">Whether to include the Ant run-time libraries in the
      classpath; defaults to <code>yes</code>, unless
      <a href="../sysclasspath.html"><code>build.sysclasspath</code></a> is set.
      <em>It is usually best to set this to false</em> so the script's behavior is not
      sensitive to the environment in which it is run.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">includeJavaRuntime</td>
    <td valign="top">Whether to include the default run-time
      libraries from the executing VM in the classpath;
      defaults to <code>no</code>.<br/>
      <b>Note:</b> In some setups the run-time libraries may be part
      of the "Ant run-time libraries" so you may need to explicitly
      set includeAntRuntime to false to ensure that the Java
      run-time libraries are not included.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">fork</td>
    <td valign="top">Whether to execute <code>javac</code> using the
      JDK compiler externally; defaults to <code>no</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">executable</td>
    <td valign="top">Complete path to the <code>javac</code>
      executable to use in case of <code>fork=&quot;yes&quot;</code>.
      Defaults to the compiler of the Java version that is currently
      running Ant.  Ignored if <code>fork=&quot;no&quot;</code>.<br>
      Since Ant 1.6 this attribute can also be used to specify the
      path to the executable when using jikes, jvc, gcj or sj.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">memoryInitialSize</td>
    <td valign="top">The initial size of the memory for the underlying VM,
      if <code>javac</code> is run externally; ignored otherwise. Defaults
      to the standard VM memory setting.
      (Examples: <code>83886080</code>, <code>81920k</code>, or
      <code>80m</code>)</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">memoryMaximumSize</td>
    <td valign="top">The maximum size of the memory for the underlying VM,
      if <code>javac</code> is run externally; ignored otherwise. Defaults
      to the standard VM memory setting.
      (Examples: <code>83886080</code>, <code>81920k</code>, or
      <code>80m</code>)</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">failonerror</td>
    <td valign="top">Indicates whether compilation errors
        will fail the build; defaults to <code>true</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">errorProperty</td>
    <td valign="top">
      The property to set (to the value "true") if compilation fails.
      <em>Since Ant 1.7.1</em>.
    </td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">source</td>

    <td valign="top">Value of the <code>-source</code> command-line
    switch; will be ignored by all implementations prior to
    <code>javac1.4</code> (or <code>modern</code> when Ant is not
    running in a 1.3 VM), <code>gcj</code> and <code>jikes</code>.<br>
    If you use this attribute together with <code>gcj</code>
    or <code>jikes</code>, you must make sure that your version
    supports the <code>-source</code> (or <code>-fsource</code> for
    gcj)
    switch.  By default, no <code>-source</code> argument will be used
    at all.<br>
    <b>Note that the default value depends on the JVM that is running
    Ant.  We highly recommend to always specify this
    attribute.</b><br>
    A default value for this attribute can be provided using the magic
    <a
    href="../javacprops.html#source"><code>ant.build.javac.source</code></a>
    property.</td>

    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">compiler</td>
    <td valign="top">The compiler implementation to use.
      If this attribute is not set, the value of the
      <code>build.compiler</code> property, if set, will be used.
      Otherwise, the default compiler for the current VM will be used.
      (See the above <a href="#compilervalues">list</a> of valid
      compilers.)</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">listfiles</td>
    <td valign="top">Indicates whether the source files to be compiled will
      be listed; defaults to <code>no</code>.</td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">tempdir</td>
    <td valign="top">Where Ant should place temporary files.
      This is only used if the task is forked and the
      command line args length exceeds 4k.
      <em>Since Ant 1.6</em>.</td>
    <td align="center" valign="top">
      No; default is <i>java.io.tmpdir</i>.
    </td>
  </tr>
  <tr>
    <td valign="top">updatedProperty</td>
    <td valign="top">
      The property to set (to the value "true") 
      if compilation has taken place
      and has been successful.
      <em>Since Ant 1.7.1</em>.
    </td>
    <td align="center" valign="top">No</td>
  </tr>
  <tr>
    <td valign="top">includeDestClasses</td>
    <td valign="top">
      This attribute controls whether to include the
      destination classes directory in the classpath
      given to the compiler.
      The default value of this is "true" and this
      means that previously compiled classes are on
      the classpath for the compiler. This means that "greedy" compilers
      will not recompile dependant classes that are already compiled.
      In general this is a good thing as it stops the compiler
      for doing unnecessary work. However, for some edge cases,
      involving generics, the javac compiler
      needs to compile the dependant classes to get the generics
      information. One example is documented in the bug report:
      <a href="http://issues.apache.org/bugzilla/show_bug.cgi?id=40776">
        Bug 40776 - a problem compiling a Java 5 project with generics</a>.
      Setting the attribute to "false" will cause the compiler
      to recompile dependent classes.
      <em>Since Ant 1.7.1</em>.
    </td>
    <td align="center" valign="top">No - default is "true"</td>
  </tr>
</table>

<h3>Parameters specified as nested elements</h3>
<p>This task forms an implicit <a href="../CoreTypes/fileset.html">FileSet</a> and
supports most attributes of <code>&lt;fileset&gt;</code>
(<code>dir</code> becomes <code>srcdir</code>) as well as the nested
<code>&lt;include&gt;</code>, <code>&lt;exclude&gt;</code> and
<code>&lt;patternset&gt;</code> elements.</p>
<h4><code>src</code>, <code>classpath</code>, <code>sourcepath</code>,
<code>bootclasspath</code> and <code>extdirs</code></h4>
<p><code>&lt;javac&gt;</code>'s <code>srcdir</code>, <code>classpath</code>,
<code>sourcepath</code>, <code>bootclasspath</code>, and
<code>extdirs</code> attributes are
<a href="../using.html#path">path-like structures</a>
and can also be set via nested
<code>&lt;src&gt;</code>,
<code>&lt;classpath&gt;</code>,
<code>&lt;sourcepath&gt;</code>,
<code>&lt;bootclasspath&gt;</code> and
<code>&lt;extdirs&gt;</code> elements, respectively.</p>

<h4>compilerarg</h4>

<p>You can specify additional command line arguments for the compiler
with nested <code>&lt;compilerarg&gt;</code> elements.  These elements
are specified like <a href="../using.html#arg">Command-line
Arguments</a> but have an additional attribute that can be used to
enable arguments only if a given compiler implementation will be
used.</p>
<table border="1" cellpadding="2" cellspacing="0">
<tr>
  <td width="12%" valign="top"><b>Attribute</b></td>
  <td width="78%" valign="top"><b>Description</b></td>
  <td width="10%" valign="top"><b>Required</b></td>
</tr>
  <tr>
    <td valign="top">value</td>
    <td align="center" rowspan="4">See
    <a href="../using.html#arg">Command-line Arguments</a>.</td>
    <td align="center" rowspan="4">Exactly one of these.</td>
  </tr>
  <tr>
    <td valign="top">line</td>
  </tr>
  <tr>
    <td valign="top">file</td>
  </tr>
  <tr>
    <td valign="top">path</td>
  </tr>
  <tr>
    <td valign="top">prefix</td>
    <td align="center" rowspan="2">See
    <a href="../using.html#arg">Command-line Arguments</a>.
    <em>Since Ant 1.8.</em></td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">suffix</td>
    <td valign="top" align="center">No</td>
  </tr>
  <tr>
    <td valign="top">compiler</td>
    <td>Only pass the specified argument if the chosen
      compiler implementation matches the value of this attribute.
      Legal values are the
      same as those in the above <a href="#compilervalues">list</a> of valid
      compilers.)</td>
    <td align="center">No</td>
  </tr>
</table>

<h4>compilerclasspath <em>since Ant 1.8.0</em></h4>

<p>A <a href="../using.html#path">PATH like structure</a> holding the
  classpath to use when loading the compiler implementation if a
  custom class has been specified.  Doesn't have any effect when
  using one of the built-in compilers.</p>


<h3>Examples</h3>
<pre>  &lt;javac srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot;
         classpath=&quot;xyz.jar&quot;
         debug=&quot;on&quot;
         source=&quot;1.4&quot;
  /&gt;</pre>
<p>compiles all <code>.java</code> files under the <code>${src}</code>
directory, and stores
the <code>.class</code> files in the <code>${build}</code> directory.
The classpath used includes <code>xyz.jar</code>, and compiling with
debug information is on. The source level is 1.4,
so you can use <code>assert</code> statements.</p>

<pre>  &lt;javac srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot;
         fork=&quot;true&quot;
         source=&quot;1.2&quot;
         target=&quot;1.2&quot;
  /&gt;</pre>
<p>compiles all <code>.java</code> files under the <code>${src}</code>
directory, and stores the <code>.class</code> files in the
<code>${build}</code> directory.  This will fork off the javac
compiler using the default <code>javac</code> executable.
The source level is 1.2 (similar to 1.1 or 1.3) and
the class files should be runnable under JDK 1.2+ as well.</p>

<pre>  &lt;javac srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot;
         fork=&quot;java$$javac.exe&quot;
         source=&quot;1.5&quot;
  /&gt;</pre>
<p>compiles all <code>.java</code> files under the <code>${src}</code>
directory, and stores the <code>.class</code> files in the
<code>${build}</code> directory.  This will fork off the javac
compiler, using the executable named <code>java$javac.exe</code>.  Note
that the <code>$</code> sign needs to be escaped by a second one.
The source level is 1.5, so you can use generics.</p>

<pre>  &lt;javac srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot;
         includes=&quot;mypackage/p1/**,mypackage/p2/**&quot;
         excludes=&quot;mypackage/p1/testpackage/**&quot;
         classpath=&quot;xyz.jar&quot;
         debug=&quot;on&quot;
  /&gt;</pre>
<p>compiles <code>.java</code> files under the <code>${src}</code>
directory, and stores the
<code>.class</code> files in the <code>${build}</code> directory.
The classpath used includes <code>xyz.jar</code>, and debug information is on.
Only files under <code>mypackage/p1</code> and <code>mypackage/p2</code> are
used. All files in and below the <code>mypackage/p1/testpackage</code>
directory are excluded from compilation.
You didn't specify a source or target level,
so the actual values used will depend on which JDK you ran Ant with.</p>

<pre>  &lt;javac srcdir=&quot;${src}:${src2}&quot;
         destdir=&quot;${build}&quot;
         includes=&quot;mypackage/p1/**,mypackage/p2/**&quot;
         excludes=&quot;mypackage/p1/testpackage/**&quot;
         classpath=&quot;xyz.jar&quot;
         debug=&quot;on&quot;
  /&gt;</pre>

<p>is the same as the previous example, with the addition of a second
source path, defined by
the property <code>src2</code>. This can also be represented using nested
<code>&lt;src&gt;</code> elements as follows:</p>

<pre>  &lt;javac destdir=&quot;${build}&quot;
         classpath=&quot;xyz.jar&quot;
         debug=&quot;on&quot;&gt;
    &lt;src path=&quot;${src}&quot;/&gt;
    &lt;src path=&quot;${src2}&quot;/&gt;
    &lt;include name=&quot;mypackage/p1/**&quot;/&gt;
    &lt;include name=&quot;mypackage/p2/**&quot;/&gt;
    &lt;exclude name=&quot;mypackage/p1/testpackage/**&quot;/&gt;
  &lt;/javac&gt;</pre>

<p>If you want to run the javac compiler of a different JDK, you
should tell Ant, where to find the compiler and which version of JDK
you will be using so it can choose the correct command line switches.
The following example executes a JDK 1.1 javac in a new process and
uses the correct command line switches even when Ant is running in a
Java VM of a different version:</p>

<pre>  &lt;javac srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot;
         fork=&quot;yes&quot;
         executable=&quot;/opt/java/jdk1.1/bin/javac&quot;
         compiler=&quot;javac1.1&quot;
  /&gt;</pre>

<p><a name="srcdirnote"><b>Note:</b></a>
If you wish to compile only source files located in certain packages below a
common root, use the <code>include</code>/<code>exclude</code> attributes
or <code>&lt;include&gt;</code>/<code>&lt;exclude&gt;</code> nested elements
to filter for these packages. Do not include part of your package structure
in the <code>srcdir</code> attribute
(or nested <code>&lt;src&gt;</code> elements), or Ant will recompile your
source files every time you run your compile target. See the
<a href="http://ant.apache.org/faq.html#always-recompiles">Ant FAQ</a>
for additional information.</p>

<p>
If you wish to compile only files explicitly specified and disable
javac's default searching mechanism then you can unset the sourcepath
attribute:
<pre>  &lt;javac sourcepath=&quot;&quot; srcdir=&quot;${src}&quot;
         destdir=&quot;${build}&quot; &gt;
    &lt;include name="**/*.java"/&gt;
    &lt;exclude name="**/Example.java"/&gt;
  &lt;/javac&gt;</pre>
That way the javac will compile all java source files under &quot;${src}&quot;
directory but skip the examples. The compiler will even produce errors if some of
the non-example files refers to them.
</p>

<p>
If you wish to compile with a special JDK (another than the one Ant is currently using),
set the <code>executable</code> and <code>fork</code> attribute. Using <code>taskname</code>
could show in the log, that these settings are fix.
<pre>  &lt;javac srcdir=&quot;&quot; 
         destdir=&quot;&quot;
         executable=&quot;path-to-java14-home/bin/javac&quot; 
         fork=&quot;true&quot;
         taskname=&quot;javac1.4&quot; /&gt;</pre>
</p>


<p><b>Note:</b> If you are using Ant on Windows and a new DOS window pops up
for every use of an external compiler, this may be a problem of the JDK you are
using.  This problem may occur with all JDKs &lt; 1.2.</p>


<p>
If you want to activate other compiler options like <i>lint</i> you could use
the <tt>&lt;compilerarg&gt;</tt> element:
<pre>  &lt;javac srcdir="${src.dir}"
         destdir="${classes.dir}"
         classpathref="libraries"&gt;
    &lt;compilerarg value="-Xlint"/&gt;
  &lt;/javac&gt; </pre>
</p>  


<h3>Jikes Notes</h3>

<p>You need Jikes 1.15 or later.</p>

<p>Jikes supports some extra options, which can be set be defining
the properties shown below prior to invoking the task. The setting
for each property will be in affect for all <code>&lt;javac&gt;</code>
tasks throughout the build.
The Ant developers are aware that
this is ugly and inflexible &ndash; expect a better solution in the future.
All the options are boolean, and must be set to <code>true</code> or
<code>yes</code> to be
interpreted as anything other than false. By default,
<code>build.compiler.warnings</code> is <code>true</code>,
while all others are <code>false</code>.</p>

<table border="1" cellpadding="2" cellspacing="0">
  <tr>
    <td valign="top"><b>Property</b></td>
    <td valign="top"><b>Description</b></td>
    <td align="center" valign="top"><b>Default</b></td>
  </tr>
  <tr>
    <td valign="top">
	build.compiler.emacs
	</td>
	<td valign="top">
	Enable emacs-compatible error messages.
    </td>
    <td valign="top">
	<code>false</code>
	</td>
  </tr>
  <tr>
    <td valign="top">
	build.compiler.fulldepend
	</td>
	<td valign="top">
	Enable full dependency checking; see<br>
	the <code>+F</code> switch in the Jikes manual.
    </td>
    <td valign="top">
	<code>false</code>
	</td>
  </tr>
  <tr>
    <td valign="top">
	build.compiler.pedantic
	</td>
	<td valign="top">
	Enable pedantic warnings.
    </td>
    <td valign="top">
	<code>false</code>
	</td>
  </tr>
  <tr>
    <td valign="top">
	build.compiler.warnings<br>
        <strong>Deprecated</strong>. Use
  <code>&lt;javac&gt;</code>'s <code>nowarn</code>
  attribute instead.
	</td>
	<td valign="top">
	Don't disable warning messages.
    </td>
    <td valign="top">
	<code>true</code>
	</td>
  </tr>
</table>

<h3>Jvc Notes</h3>

<p>Jvc will enable Microsoft extensions unless you set the property
<code>build.compiler.jvc.extensions</code> to false before invoking
<code>&lt;javac&gt;</code>.</p>

<h3><a name="bootstrap">Bootstrap Options</h3>
<p>
  The Sun javac compiler has a <em>bootclasspath</em> command
  line option - this corresponds to the "bootclasspath" attribute/element
  of the &lt;javac&gt; task. The Sun compiler also allows more
  control over the boot classpath using the -X and -J-X attributes.
  One can set these by using the &lt;compilerarg&gt;. Since Ant 1.6.0,
  there is a shortcut to convert path references to strings that
  can by used in an OS independent fashion (see
  <a href="../using.html#pathshortcut">pathshortcut</a>). For example:
</p>
<pre>
  &lt;path id="lib.path.ref"&gt;
    &lt;fileset dir="lib" includes="*.jar"/&gt;
  &lt;/path&gt;
  &lt;javac srcdir="src" destdir="classes"&gt;
    &lt;compilerarg arg="-Xbootstrap/p:${toString:lib.path.ref}"/&gt;
  &lt;/javac&gt;
</pre>

  
</p>

<h3>OpenJDK Notes</h3>
<p>
  The <a href="https://openjdk.dev.java.net/">openjdk</a>
  project has provided the javac
  <a href="https://openjdk.dev.java.net/compiler/">compiler</a>
  as an opensource project. The output of this project is a
  <code>javac.jar</code> which contains the javac compiler.
  This compiler may be used with the <code>&lt;javac&gt;</code> task with
  the use of a <code>-Xbootclasspath/p</code> java argument. The argument needs
  to be given to the runtime system of the javac executable, so it needs
  to be prepended with a "-J". For example:

<blockquote><pre>
  &lt;property name="patched.javac.jar"
            location="${my.patched.compiler}/dist/lib/javac.jar"/&gt;

  &lt;presetdef name="patched.javac"&gt;
    &lt;javac fork="yes"&gt;
      &lt;compilerarg value="-J-Xbootclasspath/p:${patched.javac.jar}"/&gt;
    &lt;/javac&gt;
  &lt;/presetdef&gt;


  &lt;patched.javac srcdir="src/java" destdir="build/classes"
                 debug="yes"/&gt;
</pre></blockquote>

  <h3>Note on package-info.java</h3>
  <p>
    <code>package-info.java</code> files were introduced in Java5 to
    allow package level annotations. On compilation, if the java file
    does not contain runtime annotations, there will be no .class file
    for the java file. Up to <b>Ant 1.7.1</b>, when the &lt;javac&gt;
    task is run again, the
    task will try to compile the package-info java files again.
  </p>
  <p>
    In <b>Ant 1.7.1</b> the package-info.java will only be compiled if:
    <ol>
      <li>
        If a <code>package-info.class</code> file exists and is older than
        the <code>package-info.java</code> file.
      </li>
      <li>
        If the directory for the 
        <code>package-info.class</code> file does not exist.
      </li>
      <li>
        If the directory for the
        <code>package-info.class</code> file exists, and has an older
        modification time than the
        the <code>package-info.java</code> file. In this case
        &lt;javac&gt; will touch the corresponding .class directory
        on successful compilation.
      </li>
    </ol>
  </p>

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