有时候 Alt+/ 的eclipse卡死，而且出现如下错误
报错内容：
The 'org.eclipse.jdt.ui.JavaAllCompletionProposalComputer' proposal computer from 'org.eclipse.jdt.ui' plug-in did not complete normally. The extension took too long to return from the 'computeCompletion Proposals()' operation.
To avoid this message, disable the 'org.eclipse.jdt.ui' plug-in or disable the 'Java Proposals' category on the content assist preference page.
点击 报错中的 “content assist”
按图中红圈，将 Java Proposals 和 Java Proposals(Task-Focused)勾选，Java Proposals(Code Recommenders)取消勾选，即可