How to set memory used by JVM in Ant

This example illustrates how to set memory size of JVM (java virtual machine), when ANT (another neat tool) is used outside of java virtual machine. In this example, <property name="sourcedir"> is used to specify the location of source directory and <property name="targetdir"> is used to specify the location of target directory and <property name="librarydir"> is used to define the location of library directory.

In this build.xml file, <path id="libraries"> is used to put any jar file in the lib directory. The target <target name="clean"> is used to delete the target directory and library directory from base directory. The target <target name="prepare"> is used to create the source directory, target directory and library directory and <target name="compile"> is used to compile the source code. The fork="true" is used if you don't run Java code in a separate JVM to the ant script, you can get some pretty strange errors that are difficult to diagnose. For NoClassDefFoundError, the problem was fixed by setting fork=true in the java target. The memoryMaximumSize="1024m" for the underlying VM, if using fork mode; ignored otherwise. Defaults to the standard VM memory setting. (Examples: 83886080, 81920k, or 80m) and memoryInitialSize="256m" is used for the underlying VM, if using fork mode; ignored otherwise. Defaults to the standard VM memory setting. (Examples: 83886080, 81920k, or 80m). The source code of build.xml file is as follows:

<project name="MemoryMap" default="compile" basedir=".">
  <property name="sourcedir" value="${basedir}/src"/>
  <property name="targetdir" value="${basedir}/build"/>
  <property name="librarydir" value="${basedir}/lib"/>

  <path id="libraries">
    <fileset dir="${librarydir}">
      <include name="*.jar"/>
    </fileset>
  </path>

    <target name="clean">
        <delete dir="${targetdir}"/>

<delete dir="${librarydir}"/>
    </target>

  <target name="prepare" depends="clean">
    <mkdir dir="${sourcedir}"/>
    <mkdir dir="${targetdir}"/>
    <mkdir dir="${librarydir}"/>
  </target>

  <target name="compile" depends="prepare">
    <javac srcdir="${sourcedir}" destdir="${targetdir}" debug="true"
      fork="true" memoryMaximumSize="1024m" memoryInitialSize="256m">
    </javac>
  </target>

</project>

Hello.java

class Hello{
        public static void main(String args[]){
                System.out.println("Sandeep kumar suman");
        }
}

Create a class file in the 'src' folder and compile it on the console with ant command. The following output will be displayed.

Download Source Code

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