trunk/docs/manual/CoreTypes/custom-programming.html - ant - Git at Google

 <!--
    Licensed to the Apache Software Foundation (ASF) under one or more
    contributor license agreements.  See the NOTICE file distributed with
    this work for additional information regarding copyright ownership.
    The ASF licenses this file to You under the Apache License, Version 2.0
    (the "License"); you may not use this file except in compliance with
    the License.  You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
 -->
 <html>
   <head>
     <meta http-equiv="Content-Language" content="en-us"></meta>
 <link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
 <title>Custom Components</title>
   </head>
   <body>
     <h2>Custom Components</h2>
     <h3>Overview</h3>
     <p>
       Custom components are conditions, selectors, filters and other
       objects that are defined outside ant core.
     </p>
     <p>
       In Ant 1.6 custom conditions, selectors and filters has
       been overhauled.
     </p>
     <p>
       It is now possible to define custom conditions, selectors and filters
       that behave like Ant Core components.
       This is achieved by allowing datatypes defined in build scripts
       to be used as custom components if the class of the datatype
       is compatible, or has been adapted by an adapter class.
     </p>
     <p>
       The old methods of defining custom components are still supported.
     </p>
     <h3>Definition and use</h3>
     <p>
       A custom component is a normal Java class that implements a particular
       interface or extends a  particular class, or has been adapted to the
       interface or class.
     </p>
     <p>
       It is exactly like writing a
       <a href="../develop.html#writingowntask">custom task</a>.
       One defines attributes and nested elements by writing <i>setter</i>
       methods and <i>add</i> methods.
     </p>
     <p>
       After the class has been written, it is added to the ant system
       by using <code>&lt;typedef&gt;</code>.
     </p>
     <h3><a name="customconditions">Custom Conditions</a></h3>
     <p>
       Custom conditions are datatypes that implement
       <code>org.apache.tools.ant.taskdefs.condition.Condition</code>.
       For example a custom condition that returns true if a
       string is all upper case could be written as:
     </p>
     <blockquote>
       <pre>
 package com.mydomain;

 import org.apache.tools.ant.BuildException;
 import org.apache.tools.ant.taskdefs.condition.Condition;

 public class AllUpperCaseCondition implements Condition {
     private String value;

     // The setter for the "value" attribute
     public void setValue(String value) {
         this.value = value;
     }

     // This method evaluates the condition
     public boolean eval() {
         if (value == null) {
             throw new BuildException("value attribute is not set");
         }
         return value.toUpperCase().equals(value);
    }
 }
       </pre>
     </blockquote>

     <p>
         Adding the condition to the system is achieved as follows:
     </p>
     <blockquote>
       <pre>
 &lt;typedef
     name="alluppercase"
     classname="com.mydomain.AllUpperCaseCondition"
     classpath="${mydomain.classes}"/&gt;
       </pre>
     </blockquote>
     <p>
       This condition can now be used wherever a Core Ant condition
       is used.
     </p>
     <blockquote>
       <pre>
 &lt;condition property="allupper"&gt;
    &lt;alluppercase value="THIS IS ALL UPPER CASE"/&gt;
 &lt;/condition&gt;
       </pre>
     </blockquote>
     <h3><a name="customselectors">Custom Selectors</a></h3>
     <p>
       Custom selectors are datatypes that implement
       <code>org.apache.tools.ant.types.selectors.FileSelector</code>.
     </p>
     <p>There is only one method required.
       <code>public boolean isSelected(File basedir, String filename,
         File file)</code>.
       It returns true
       or false depending on whether the given file should be
       selected or not.
     </p>
     <p>
       An example of a custom selection that selects filenames ending
       in ".java" would be:
     </p>
     <blockquote>
       <pre>
 package com.mydomain;
 import java.io.File;
 import org.apache.tools.ant.types.selectors.FileSelector;
 public class JavaSelector implements FileSelector {
     public boolean isSelected(File b, String filename, File f) {
        return filename.toLowerCase().endsWith(".java");
     }
 }
       </pre>
     </blockquote>
     <p>
       Adding the selector to the system is achieved as follows:
     </p>
     <blockquote>
       <pre>
 &lt;typedef
     name="javaselector"
     classname="com.mydomain.JavaSelector"
     classpath="${mydomain.classes}"/&gt;
       </pre>
     </blockquote>
         <p>
       This selector can now be used wherever a Core Ant selector
       is used, for example:
     </p>
     <blockquote>
       <pre>
 &lt;copy todir="to"&gt;
    &lt;fileset dir="src"&gt;
       &lt;javaselector/&gt;
    &lt;/fileset&gt;
 &lt;/copy&gt;
       </pre>
     </blockquote>

       <p>
         One may use
         <code>org.apache.tools.ant.types.selectors.BaseSelector</code>,
         a convenience class that provides reasonable default
         behaviour.
         It has some predefined behaviours you can take advantage
         of. Any time you encounter a problem when setting attributes or
         adding tags, you can call setError(String errmsg) and the class
         will know that there is a problem. Then, at the top of your
         <code>isSelected()</code> method call <code>validate()</code> and
         a BuildException will be thrown with the contents of your error
         message. The <code>validate()</code> method also gives you a
         last chance to check your settings for consistency because it
         calls <code>verifySettings()</code>. Override this method and
         call <code>setError()</code> within it if you detect any
         problems in how your selector is set up.
     </p>
     <p>
       To write custom selector containers one should extend
       <code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>.
       Implement the
       <code>public boolean isSelected(File baseDir, String filename, File file)</code>
       method to do the right thing. Chances are you'll want to iterate
       over the selectors under you, so use
       <code>selectorElements()</code> to get an iterator that will do
       that.
     </p>
     <p>
       For example to create a selector container that will select files
       if a certain number of contained selectors select, one could write
       a selector as follows:
     </p>
     <blockquote>
       <pre>
 public class MatchNumberSelectors extends BaseSelectorContainer {
     private int number = -1;
     public void setNumber(int number) {
         this.number = number;
     }
     public void verifySettings() {
         if (number &lt; 0) {
            throw new BuildException("Number attribute should be set");
         }
     }
     public boolean isSelected(File baseDir, String filename, File file) {
         validate();
         int numberSelected = 0;
         for (Enumeration e = selectorElements(); e.hasNextElement();) {
             FileSelector s = (FileSelector) e.nextElement();
             if (s.isSelected(baseDir, filename, file)) {
                 numberSelected++;
             }
         }
         return numberSelected == number;
     }
 }
       </pre>
     </blockquote>
     <p>
       To define and use this selector one could do:
     </p>
     <blockquote>
       <pre>
 &lt;typedef name="numberselected"
          classname="com.mydomain.MatchNumberSelectors"/&gt;
 ...
 &lt;fileset dir="${src.path}"&gt;
    &lt;numberselected number="2"&gt;
       &lt;contains text="script" casesensitive="no"/&gt;
       &lt;size value="4" units="Ki" when="more"/&gt;
       &lt;javaselector/&gt;
    &lt;/numberselected&gt;
 &lt;/fileset&gt;
       </pre>
     </blockquote>
     <p>
       <i>The custom selector</i>
     </p>
     <p>
       The custom selector was the pre ant 1.6 way of defining custom selectors.
       This method is still supported for backward compatibility.
     </p>
     <p>You can write your own selectors and use them within the selector
       containers by specifying them within the <code>&lt;custom&gt;</code> tag.</p>

         <p>To create a new Custom Selector, you have to create a class that
         implements
         <code>org.apache.tools.ant.types.selectors.ExtendFileSelector</code>.
         The easiest way to do that is through the convenience base class
         <code>org.apache.tools.ant.types.selectors.BaseExtendSelector</code>,
         which provides all of the methods for supporting
         <code>&lt;param&gt;</code> tags. First, override the
         <code>isSelected()</code> method, and optionally the
         <code>verifySettings()</code> method. If your custom
         selector requires parameters to be set, you can also override
         the <code>setParameters()</code> method and interpret the
         parameters that are passed in any way you like. Several of the
         core selectors demonstrate how to do that because they can
         also be used as custom selectors.</p>


     <p>Once that is written, you include it in your build file by using
       the <code>&lt;custom&gt;</code> tag.
     </p>

     <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">classname</td>
         <td valign="top">The name of your class that implements
           <code>org.apache.tools.ant.types.selectors.FileSelector</code>.
         </td>
         <td valign="top" align="center">Yes</td>
       </tr>
       <tr>
         <td valign="top">classpath</td>
         <td valign="top">The classpath to use in order to load the
           custom selector class. If neither this classpath nor the
           classpathref are specified, the class will be
           loaded from the classpath that Ant uses.
         </td>
         <td valign="top" align="center">No</td>
       </tr>
       <tr>
         <td valign="top">classpathref</td>
         <td valign="top">A reference to a classpath previously
           defined. If neither this reference nor the
           classpath above are specified, the class will be
           loaded from the classpath that Ant uses.
         </td>
         <td valign="top" align="center">No</td>
       </tr>
     </table>

     <p>Here is how you use <code>&lt;custom&gt;</code> to
       use your class as a selector:
     </p>

     <blockquote><pre>
 &lt;fileset dir="${mydir}" includes="**/*"&gt;
     &lt;custom classname="com.mydomain.MySelector"&gt;
         &lt;param name="myattribute" value="myvalue"/&gt;
     &lt;/custom&gt;
 &lt;/fileset&gt;
       </pre></blockquote>


     <p>The core selectors that can also be used as custom selectors
       are</p>

     <ul>
       <li><a href="selectors.html#containsselect">Contains Selector</a> with
         classname <code>org.apache.tools.ant.types.selectors.ContainsSelector</code>
       </li>
       <li><a href="selectors.html#dateselect">Date Selector</a> with
         classname <code>org.apache.tools.ant.types.selectors.DateSelector</code>
       </li>
       <li><a href="selectors.html#depthselect">Depth Selector</a> with
         classname <code>org.apache.tools.ant.types.selectors.DepthSelector</code>
       </li>
       <li><a href="selectors.html#filenameselect">Filename Selector</a> with
         classname <code>org.apache.tools.ant.types.selectors.FilenameSelector</code>
       </li>
       <li><a href="selectors.html#sizeselect">Size Selector</a> with
         classname <code>org.apache.tools.ant.types.selectors.SizeSelector</code>
       </li>
     </ul>

     <p>Here is the example from the Depth Selector section rewritten
     to use the selector through <code>&lt;custom&gt;</code>.</p>

     <blockquote><pre>
 &lt;fileset dir="${doc.path}" includes="**/*"&gt;
     &lt;custom classname="org.apache.tools.ant.types.selectors.DepthSelector"&gt;
         &lt;param name="max" value="1"/&gt;
     &lt;/custom&gt;
 &lt;/fileset&gt;
       </pre></blockquote>

     <p>Selects all files in the base directory and one directory below
       that.</p>

     <h3><a name="filterreaders">Custom Filter Readers</a></h3>
     <p>
       Custom filter readers selectors are datatypes that implement
       <code>org.apache.tools.ant.types.filters.ChainableReader</code>.
     </p>
     <p>There is only one method required.
       <code>Reader chain(Reader reader)</code>.
       This returns a reader that filters input from the specified
       reader.
     </p>
     <p>
       For example a filterreader that removes every second character
       could be:
     </p>
     <blockquote>
       <pre>
 public class RemoveOddCharacters implements ChainableReader {
    public Reader chain(Reader reader) {
       return new BaseFilterReader(reader) {
           int count = 0;
           public int read() throws IOException {
               while (true) {
                 int c = in.read();
                 if (c == -1) {
                     return c;
                 }
                 count++;
                 if ((count % 2) == 1) {
                     return c;
                 }
               }
           }
       }
    }
 }
       </pre>
     </blockquote>
     <p>
       For line oriented filters it may be easier to extend
       <code>ChainableFilterReader</code> an inner class of
       <code>org.apache.tools.ant.filters.TokenFilter</code>.
     </p>
     <p>
       For example a filter that appends the line number could be
     </p>
     <blockquote>
       <pre>
 public class AddLineNumber extends ChainableReaderFilter {
    private void lineNumber = 0;
    public String filter(String string) {
       lineNumber++;
       return "" + lineNumber + "\t" + string;
    }
 }
       </pre>
     </blockquote>


     <hr></hr>
   </body>
 </html>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<html>
	<head>
	<meta http-equiv="Content-Language" content="en-us"></meta>
	<link rel="stylesheet" type="text/css" href="../stylesheets/style.css">
	<title>Custom Components</title>
	</head>
	<body>
	<h2>Custom Components</h2>
	<h3>Overview</h3>
	<p>
	Custom components are conditions, selectors, filters and other
	objects that are defined outside ant core.
	</p>
	<p>
	In Ant 1.6 custom conditions, selectors and filters has
	been overhauled.
	</p>
	<p>
	It is now possible to define custom conditions, selectors and filters
	that behave like Ant Core components.
	This is achieved by allowing datatypes defined in build scripts
	to be used as custom components if the class of the datatype
	is compatible, or has been adapted by an adapter class.
	</p>
	<p>
	The old methods of defining custom components are still supported.
	</p>
	<h3>Definition and use</h3>
	<p>
	A custom component is a normal Java class that implements a particular
	interface or extends a particular class, or has been adapted to the
	interface or class.
	</p>
	<p>
	It is exactly like writing a
	<a href="../develop.html#writingowntask">custom task</a>.
	One defines attributes and nested elements by writing <i>setter</i>
	methods and <i>add</i> methods.
	</p>
	<p>
	After the class has been written, it is added to the ant system
	by using <code><typedef></code>.
	</p>
	<h3><a name="customconditions">Custom Conditions</a></h3>
	<p>
	Custom conditions are datatypes that implement
	<code>org.apache.tools.ant.taskdefs.condition.Condition</code>.
	For example a custom condition that returns true if a
	string is all upper case could be written as:
	</p>
	<blockquote>
	<pre>
	package com.mydomain;

	import org.apache.tools.ant.BuildException;
	import org.apache.tools.ant.taskdefs.condition.Condition;

	public class AllUpperCaseCondition implements Condition {
	private String value;

	// The setter for the "value" attribute
	public void setValue(String value) {
	this.value = value;
	}

	// This method evaluates the condition
	public boolean eval() {
	if (value == null) {
	throw new BuildException("value attribute is not set");
	}
	return value.toUpperCase().equals(value);
	}
	}
	</pre>
	</blockquote>

	<p>
	Adding the condition to the system is achieved as follows:
	</p>
	<blockquote>
	<pre>
	<typedef
	name="alluppercase"
	classname="com.mydomain.AllUpperCaseCondition"
	classpath="${mydomain.classes}"/>
	</pre>
	</blockquote>
	<p>
	This condition can now be used wherever a Core Ant condition
	is used.
	</p>
	<blockquote>
	<pre>
	<condition property="allupper">
	<alluppercase value="THIS IS ALL UPPER CASE"/>
	</condition>
	</pre>
	</blockquote>
	<h3><a name="customselectors">Custom Selectors</a></h3>
	<p>
	Custom selectors are datatypes that implement
	<code>org.apache.tools.ant.types.selectors.FileSelector</code>.
	</p>
	<p>There is only one method required.
	<code>public boolean isSelected(File basedir, String filename,
	File file)</code>.
	It returns true
	or false depending on whether the given file should be
	selected or not.
	</p>
	<p>
	An example of a custom selection that selects filenames ending
	in ".java" would be:
	</p>
	<blockquote>
	<pre>
	package com.mydomain;
	import java.io.File;
	import org.apache.tools.ant.types.selectors.FileSelector;
	public class JavaSelector implements FileSelector {
	public boolean isSelected(File b, String filename, File f) {
	return filename.toLowerCase().endsWith(".java");
	}
	}
	</pre>
	</blockquote>
	<p>
	Adding the selector to the system is achieved as follows:
	</p>
	<blockquote>
	<pre>
	<typedef
	name="javaselector"
	classname="com.mydomain.JavaSelector"
	classpath="${mydomain.classes}"/>
	</pre>
	</blockquote>
	<p>
	This selector can now be used wherever a Core Ant selector
	is used, for example:
	</p>
	<blockquote>
	<pre>
	<copy todir="to">
	<fileset dir="src">
	<javaselector/>
	</fileset>
	</copy>
	</pre>
	</blockquote>

	<p>
	One may use
	<code>org.apache.tools.ant.types.selectors.BaseSelector</code>,
	a convenience class that provides reasonable default
	behaviour.
	It has some predefined behaviours you can take advantage
	of. Any time you encounter a problem when setting attributes or
	adding tags, you can call setError(String errmsg) and the class
	will know that there is a problem. Then, at the top of your
	<code>isSelected()</code> method call <code>validate()</code> and
	a BuildException will be thrown with the contents of your error
	message. The <code>validate()</code> method also gives you a
	last chance to check your settings for consistency because it
	calls <code>verifySettings()</code>. Override this method and
	call <code>setError()</code> within it if you detect any
	problems in how your selector is set up.
	</p>
	<p>
	To write custom selector containers one should extend
	<code>org.apache.tools.ant.types.selectors.BaseSelectorContainer</code>.
	Implement the
	<code>public boolean isSelected(File baseDir, String filename, File file)</code>
	method to do the right thing. Chances are you'll want to iterate
	over the selectors under you, so use
	<code>selectorElements()</code> to get an iterator that will do
	that.
	</p>
	<p>
	For example to create a selector container that will select files
	if a certain number of contained selectors select, one could write
	a selector as follows:
	</p>
	<blockquote>
	<pre>
	public class MatchNumberSelectors extends BaseSelectorContainer {
	private int number = -1;
	public void setNumber(int number) {
	this.number = number;
	}
	public void verifySettings() {
	if (number < 0) {
	throw new BuildException("Number attribute should be set");
	}
	}
	public boolean isSelected(File baseDir, String filename, File file) {
	validate();
	int numberSelected = 0;
	for (Enumeration e = selectorElements(); e.hasNextElement();) {
	FileSelector s = (FileSelector) e.nextElement();
	if (s.isSelected(baseDir, filename, file)) {
	numberSelected++;
	}
	}
	return numberSelected == number;
	}
	}
	</pre>
	</blockquote>
	<p>
	To define and use this selector one could do:
	</p>
	<blockquote>
	<pre>
	<typedef name="numberselected"
	classname="com.mydomain.MatchNumberSelectors"/>
	...
	<fileset dir="${src.path}">
	<numberselected number="2">
	<contains text="script" casesensitive="no"/>
	<size value="4" units="Ki" when="more"/>
	<javaselector/>
	</numberselected>
	</fileset>
	</pre>
	</blockquote>
	<p>
	<i>The custom selector</i>
	</p>
	<p>
	The custom selector was the pre ant 1.6 way of defining custom selectors.
	This method is still supported for backward compatibility.
	</p>
	<p>You can write your own selectors and use them within the selector
	containers by specifying them within the <code><custom></code> tag.</p>

	<p>To create a new Custom Selector, you have to create a class that
	implements
	<code>org.apache.tools.ant.types.selectors.ExtendFileSelector</code>.
	The easiest way to do that is through the convenience base class
	<code>org.apache.tools.ant.types.selectors.BaseExtendSelector</code>,
	which provides all of the methods for supporting
	<code><param></code> tags. First, override the
	<code>isSelected()</code> method, and optionally the
	<code>verifySettings()</code> method. If your custom
	selector requires parameters to be set, you can also override
	the <code>setParameters()</code> method and interpret the
	parameters that are passed in any way you like. Several of the
	core selectors demonstrate how to do that because they can
	also be used as custom selectors.</p>


	<p>Once that is written, you include it in your build file by using
	the <code><custom></code> tag.
	</p>

	<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">classname</td>
	<td valign="top">The name of your class that implements
	<code>org.apache.tools.ant.types.selectors.FileSelector</code>.
	</td>
	<td valign="top" align="center">Yes</td>
	</tr>
	<tr>
	<td valign="top">classpath</td>
	<td valign="top">The classpath to use in order to load the
	custom selector class. If neither this classpath nor the
	classpathref are specified, the class will be
	loaded from the classpath that Ant uses.
	</td>
	<td valign="top" align="center">No</td>
	</tr>
	<tr>
	<td valign="top">classpathref</td>
	<td valign="top">A reference to a classpath previously
	defined. If neither this reference nor the
	classpath above are specified, the class will be
	loaded from the classpath that Ant uses.
	</td>
	<td valign="top" align="center">No</td>
	</tr>
	</table>

	<p>Here is how you use <code><custom></code> to
	use your class as a selector:
	</p>

	<blockquote><pre>
	<fileset dir="${mydir}" includes="*/">
	<custom classname="com.mydomain.MySelector">
	<param name="myattribute" value="myvalue"/>
	</custom>
	</fileset>
	</pre></blockquote>


	<p>The core selectors that can also be used as custom selectors
	are</p>

	<ul>
	<li><a href="selectors.html#containsselect">Contains Selector</a> with
	classname <code>org.apache.tools.ant.types.selectors.ContainsSelector</code>
	</li>
	<li><a href="selectors.html#dateselect">Date Selector</a> with
	classname <code>org.apache.tools.ant.types.selectors.DateSelector</code>
	</li>
	<li><a href="selectors.html#depthselect">Depth Selector</a> with
	classname <code>org.apache.tools.ant.types.selectors.DepthSelector</code>
	</li>
	<li><a href="selectors.html#filenameselect">Filename Selector</a> with
	classname <code>org.apache.tools.ant.types.selectors.FilenameSelector</code>
	</li>
	<li><a href="selectors.html#sizeselect">Size Selector</a> with
	classname <code>org.apache.tools.ant.types.selectors.SizeSelector</code>
	</li>
	</ul>

	<p>Here is the example from the Depth Selector section rewritten
	to use the selector through <code><custom></code>.</p>

	<blockquote><pre>
	<fileset dir="${doc.path}" includes="*/">
	<custom classname="org.apache.tools.ant.types.selectors.DepthSelector">
	<param name="max" value="1"/>
	</custom>
	</fileset>
	</pre></blockquote>

	<p>Selects all files in the base directory and one directory below
	that.</p>

	<h3><a name="filterreaders">Custom Filter Readers</a></h3>
	<p>
	Custom filter readers selectors are datatypes that implement
	<code>org.apache.tools.ant.types.filters.ChainableReader</code>.
	</p>
	<p>There is only one method required.
	<code>Reader chain(Reader reader)</code>.
	This returns a reader that filters input from the specified
	reader.
	</p>
	<p>
	For example a filterreader that removes every second character
	could be:
	</p>
	<blockquote>
	<pre>
	public class RemoveOddCharacters implements ChainableReader {
	public Reader chain(Reader reader) {
	return new BaseFilterReader(reader) {
	int count = 0;
	public int read() throws IOException {
	while (true) {
	int c = in.read();
	if (c == -1) {
	return c;
	}
	count++;
	if ((count % 2) == 1) {
	return c;
	}
	}
	}
	}
	}
	}
	</pre>
	</blockquote>
	<p>
	For line oriented filters it may be easier to extend
	<code>ChainableFilterReader</code> an inner class of
	<code>org.apache.tools.ant.filters.TokenFilter</code>.
	</p>
	<p>
	For example a filter that appends the line number could be
	</p>
	<blockquote>
	<pre>
	public class AddLineNumber extends ChainableReaderFilter {
	private void lineNumber = 0;
	public String filter(String string) {
	lineNumber++;
	return "" + lineNumber + "\t" + string;
	}
	}
	</pre>
	</blockquote>


	<hr></hr>
	</body>
	</html>