原文地址：http://blog.csdn.net/jiangtaoking/article/details/49151763

Could not find the main class: org.eclipse.ant.internal.launching.remote.InternalAntRunner. 最近更新了eclipse，发现运行ant不好使来了，报的异常如标题所示。然后各种百度，尼玛！我只想说百度上写这些bug文档的人，能不能别乱写啊，艹。按照上面所说各种尝试，都不行。没办法，还是去Google吧。

I just installed Mars and when I tried to execute a build.xml after checking out an existing and working project I got that error message:

Could not find the main class: org.eclipse.ant.internal.launching.remote.InternalAntRunner. Program will exit.

The solution is to go to Run as → External tools configuration… → JRE where the default was set to “Separate JDK”: jdk1.6.0_31 (I had set up JDKs 6-8 in Preferences after installing). I changed this to “run in the same JRE as the workspace” and now it works.

Bug fix would be to provide a working default configuration with setup. Configuration should be in a way it does not break if the user adds additional JDKs to Preferences.

原文地址：https://bugs.eclipse.org/bugs/show_bug.cgi?id=472599。噢啦，问题搞定！

翻译:右键build.xml文件Run as里选择External Tools Configuration…