可能重复：
Running application in netbeans results in NoSuchMethodError
当我在Netbeans 6.9.1中运行一个简单的应用程序时，它显示task running很长一段时间。当我点击cancel process时它没有关闭。当我点击它时，netbeans底部还有一个错误unexpected exception--> java.lang.NoSuchMethodError: org.apache.tools.ant.util：
A java.lang.NoSuchMethodError exception has occurred.
Please report this at http://www.netbeans.org/community/issues.html,
including a copy of your messages.log file as an attachment.
The messages.log file is located in your C:\Users\dell\.netbeans\6.9\var\log folder.
请帮忙