build.xml

<project name="Balls" default="jar">
    <target name="init">
        <property name="sourceDir" value="src"/>
        <property name="outputDir" value="bin"/>
        <property name="jarDir" value="jar"/>
        <property name="jarFile" value="Balls.jar"/>
    </target>

    <target name="jar" depends="build">
        <jar destfile="${jarDir}/${jarFile}">
            <fileset dir="${outputDir}"/>
            <manifest>
                <attribute name="Main-Class" value="BallGui"/>
            </manifest>
        </jar>
    </target>

    <target name="build" depends="init">
        <mkdir dir="${outputDir}"/> 
        <javac srcdir="${sourceDir}" destdir="${outputDir}"
            includeantruntime="false"/>
    </target>

    <target name="run" depends="jar">
        <java jar="${jarDir}/${jarFile}" fork="true"/>
    </target>

    <target name="runargs" depends="jar">
        <java jar="${jarDir}/${jarFile}" fork="true">
            <arg line="${args}"/>
        </java>
    </target>

    <target name="clean" depends="init">
        <delete dir="${outputDir}" quiet="true"/>
        <delete dir="${jarDir}" quiet="true"/>
    </target>
</project>