I\'m using Ant 1.7.0 and installed java 1.6 which is in JAVA_HOME.
I want to build a project using java 1.5, so I\'ve exported JAVA_HOME to be my java 1.5 directory.
By default the Ant will considered the JRE as the workspace JRE version. You need to change according to your required version by following the below.
In Eclipse:
Right click on your build.xml click "Run As", click on "External Tool Configurations..." Select tab JRE.
Select the JRE you are using.
Re-run the task, it should be fine now.