when building Appinventor source code using command "ant",there is an error

[uzumaki naruto]

I download source code from https://github.com/mit-cml/appinventor-sources;
bulid code according to https://docs.google.com/document/pub?id=1Xc9yt02x3BRoq5m1PJHBr81OOv69rEBy8LVG_84j9jc#h.3aibbept75tt;
my java version is 1.7.0_80;ant version is 1.8.1;os is 64bit Ubuntu 18.04.2.

when I input command "ant" in the shell,the error info is:

How should I do to solve this problem?
Thanks

[Chris Ward]

Hi uzumaki

This is the wrong forum for your question but my first thought is that the Java version on your PC might need an upgrade.

Please post your question on this forum:

https://groups.google.com/forum/#!forum/app-inventor-open-source-dev

[uzumaki naruto]

Hi Chris,

Thanks for your advice.