Ant using different java version during

I am trying to compile a project in java 1.6. In system the default version is 1.7. I have used below properties in build.xml but still its using java 1.7.

<property name="JAVA_VERSION"  value="1.6"/>
<property name="javahome" location="C:\Java\jdk1.6.0_45"/>
<property name="JAVA_HOME" value="C:\Java\jdk1.6.0_45\" />


<path id="wls.classpath">
		<pathelement location="${JAVA_HOME}\lib\tools.jar"/>
	</path>

<target name="compile" depends="prepare" description="compile the Java source.">
	<echo message=" java versoin is ${java.version}" />
    <javac debug="${debug}" srcdir="./src" destdir="./classes" includeAntRuntime="false" target="1.6" source="1.6">
      <classpath refid="classpath"/>
    </javac>
  </target>

Output is :

compile:
     [echo]  java versoin is 1.7.0_221
    [javac] Compiling 59 source files to C:\Jenkins\jobs\calcmanageronprem\branches\users-nageswar-k-b-test.g7m3im\workspace\CalcMgrCDF\classes
    [javac] warning: [options] bootstrap class path not set in conjunction with -source 1.6
    [javac] Note: C:\Jenkins\jobs\calcmanageronprem\branches\users-nageswar-k-b-test.g7m3im\workspace\CalcMgrCDF\src\com\hyperion\planning\formula\TimeDate.java uses or overrides a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.
    [javac] 1 warning

Please help me in using java version 1.6 to compile the code

Properties in ant only assign values to variables. Setting environment variables in system needs to be done by either batch commands or if we are using jenkins then it should be done through jenkins file as mentioned below.

Jenkins file

env.JAVA_HOME="C:/java/jdk1.6.0_45"
env.JDK_HOME="C:/java/jdk1.6.0_45"

ant file

<property environment="env"/>
<property name="javahome" location="${env.JAVA_HOME}"/>
<property name="JAVA_HOME" value="${env.JDK_HOME}" />