It seems that on some versions of NetBeans there is a parameter that sets a delay for the popup.
- Select "Tools" | Options
- Choose advanced options
- Open the "Edit" and "Settings" folders
- Select the Java Editor and find the "Delay Delay" property. Auto Popup
- Enter a new delay value in milliseconds (default is 250).
Article in which I found it: http://www.informit.com/articles/article.aspx?p=519945&seqNum=5
The problem is that this article is a couple of years old, so I opened NetBeans (6.1) on my computer and looked for a property, but this was not for the Java editor (this was done for other editors such as the XML Editor). This leads me to believe that my version is newer than the one in the article, and the delay property no longer exists for the Java editor (verification could not hurt).
So instead, I decided to check the delay. I made a sample project, imported and instantiated the list, and then made a method call. I stopped at a point to allow NetBeans to offer suggestions, and that was mostly immediate (no noticeable delay). It is at this moment that I am wondering if the delay you are experiencing is solely for the performance of the computer, especially since you indicate that this happens “sometimes”. You might be looking at fairly large classes, and NetBeans is taking the extra time to look for completions. You can try and check whether this is true or not by checking for code completion in a well-known large class. Another possibility is that your computer does not work as fast or is simultaneously working on another program. You can try and test this by restarting your computer, opening only NetBeans (to maximize resources for NetBeans) and try some code improvements. If they exhibit noticeably faster delays, this is most likely a problem.
Hope this helps.