build.xml

<?xml version="1.0"?>
<project name="Compress and minify CSS and JS" default="initialize">

  <target name="concat_css">
      <concat destfile="${assets_dir}/style.min.css">
          <filelist id="files" dir="${css_dir}">
            <file name="bootstrap.css" /> 
            <file name="bootstrap-responsive.css" /> 
            <file name="main.css" /> 
        </filelist>
      </concat>
  </target>
  
    <target name="concat_js">
      <concat destfile="${assets_dir}/script.min.js">
          <filelist id="files" dir="${js_dir}">
            <file name="bootstrap.js" /> 
            <file name="easyscroll.js" /> 
            <file name="main.js" /> 
        </filelist>
      </concat>
  </target>
  
  <property environment="env" />
  <property name="antlib_dir" value="${env.ANT_HOME}/lib" />
  
  <property name="assets_dir" value="assets" />
  <property name="js_dir" value="${assets_dir}/js" />
  <property name="css_dir" value="${assets_dir}/css" />
  
  <target name="compress">
    <java jar="${antlib_dir}/yuicompressor-2.4.7.jar" fork="true">
        <arg value="${file}" />
        <arg value="-o" />
        <arg value="${file}" />
    </java>
    <echo>${file}</echo> 
</target>

<target name="compress_css" depends="concat_css">
    <antcall target="compress">
        <param name="file" value="${assets_dir}/style.min.css" />
    </antcall>
    <checksum file="${assets_dir}/style.min.css"/>
</target>

<target name="compress_js" depends="concat_js">
    <antcall target="compress">
        <param name="file" value="${assets_dir}/script.min.js" />
    </antcall>
    <checksum file="${assets_dir}/script.min.js"/>
</target>
 
 <target name="initialize">
    <antcall target="compress_css" />
    <antcall target="compress_js" />
    <echo>Done!</echo>
</target>
 
</project>