Eclipse save automatically

Eclipse Neon (4.6)

Window > Preferences

General > Editors > Autosave > check Enable autosave for dirty editors > choose the value for autosave interval (in seconds)

Details in M7:

Auto-save of dirty editors is now available in Eclipse. The autosave option is disabled by default. A new autosave preference page (Preferences > General > Editors > Autosave) is available and allows to enable/disable the autosave and change the interval of autosave. The countdown is reset on keyboard activity, mouse click, or when a popup is displayed (e.g. content assist, preference page, ...).

You can go here and check the box Save automatically before build

Windows > Preferences > General -> Workspace

First, try Window -> Preferences -> General -> Workspace. There you can check "Save automatically before build" and "Build automatically."

If that does not work,

PLEASE TRY

Preferences -> Run/Debug -> Launching -> "Save dirty editors before launching"

You can do it with the saveDirtyEditor plugin as referenced in this question/answer. There is no non-plugin way of doing it.