Here are core problems that cause grief, raise support calls, and how to fix them.
After installing, a quick test of Ant makes sure that everything is well.
ant
ant -version
The version printed must match what you have installed
{{{> ant -version Apache Ant version 1.7alpha compiled on May 24 2005}}}
If there is a different version printed, you have an old version somewhere.
ant -diagnostics
This triggers a deep analysis and health check of Ant and its environment. Things tested include
Badly configured CLASSPATH environments cause no end of grief. Ant does not need a classpath, and nor should other modern Java programs. Make sure the environment variable is unset or empty. You can run Ant without the contents of CLASSPATH by going ant -noclasspath
You should not have quotes inside your CLASSPATH variable. It is an error to do so. It is acceptable to have spaces at the beginning and end of the variable, if you have spaces in directory names. Better yet: Do not install stuff into directories with spaces.
The JPackage team package up Ant and release it as an RPM, which is then redistributed in Linux distros such as RedHat and SuSE. If you want this integration/configuration management system, stick with it. Do not mix JPackage and Ant distributions. In particular, if you want to upgrade a JPackage installation, check the JPackage site for a new release, or remove their distribution and install Ant by hand.
Many of Ant's tasks depend on third party libraries. Ant does not include any of these, other than the Xerces XML parser. It is not enough to have the relevant optional JAR, such as "ant-junit.jar", you need the library that it depends upon, in this case "junit.jar". Similarly, it is not enough to have junit somewhere on your hard drive; ant is not going to look for it. JAR files must be
No third party JARs, no third party tasks.