Error in buildxml

I'm getting the following error when i ant run. 

also I have attached my testng.xml and build.xml files.

[javac] If you specify -target 1.6 you now must also specify -source 1.6.
[javac] Ant will implicitly add -source 1.6 for you. Please change your build file.
[javac] warning: [options] bootstrap class path not set in conjunction with -source 6
[javac] warning: [options] source value 6 is obsolete and will be removed in a future release
[javac] warning: [options] target value 1.6 is obsolete and will be removed in a future release
[javac] warning: [options] To suppress warnings about obsolete options, use -Xlint:-options.
[javac] 4 warnings

run:
[testng] Error: Unable to initialize main class org.testng.TestNG
[testng] Caused by: java.lang.NoClassDefFoundError: com/beust/jcommander/ParameterException
[testng] The tests failed.