This feature is provided by the Code Recommenders plugin. It ships with Eclipse Luna for Java SE, but for some reason it does not ship in the EE version. Of course, you can install it manually from the eclipse market.
To activate it, go to Window -> Preferences -> Code Recommenders -> Completions -> Check to enable intelligent code completion. You can also choose which type of terminations you are interested in. The exact function you are looking for is called "Subword Completion Processor" (and I can't live without it: D)

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