the 'org.eclipse.jdt.ui.javaallcompletionproposalcomputer' proposal computer from the 'org.eclipse.jdt.ui' plug-in did not complete normally......
Note that Mylyn should only add a trivial amount of overhead to content assist computation, however, the standard content assist mechanism will not report timeouts of this sort (i.e. taking longer than 5s to compute proposals).
If the system that you are working on is so large that increasing memory does not reduce the timings to avoid the message, you could also consider disabling the Mylyn-specific content assist
还有人说，Build path中引入了不是jar包的文件，比如说txt、html,xml等非jar文件的其他文件，去掉这些没用的东西就可以。可当前项目的Build path没有非jar的文件。
最后采用的解决方法是，在Window->preference->java->editor>Content Assist->advanced ，将 time out 由50 ms 改成 200 ms。