while compiling ant dist its not able to launch the ant and its giving error.

error:
$ ant dist
Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/tools/ant/launch/Launcher
Caused by: java.lang.ClassNotFoundException: org.apache.tools.ant.launch.Launcher
at java.net.URLClassLoader$1.run(URLClassLoader.java:202)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:190)
at java.lang.ClassLoader.loadClass(ClassLoader.java:307)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301)
at java.lang.ClassLoader.loadClass(ClassLoader.java:248)
Could not find the main class: org.apache.tools.ant.launch.Launcher. Program will exit.
Build step 'Invoke Ant' marked build as failure

please check the issue and reply as soon as possible.
and i tried setting both JAVA_HOME and ANT_HOME still giving the same error.