Another useful preference:

I never cared for the default AutoComplete in Eclipse. For example, suppose you have...

    System.out.print("");

and decide you want to change it to println instead of print...

    System.out.println("");

Of course you'd just insert 'ln' at the end of 'print' but to illustrate a point - if you were to select '.print' and type '.' to bring up the AutoComplete, then select 'println' and hit the enter key, you would get the following:

    System.out.println()("");

... and I would always find myself having to remove the extra parens '()' or make some other change depending on the method. This can be fixed by going to:

    Window > Preferences

and on the preferences tree select...

    Java > Editor > Content Assist : Insertion > Completion overwrites

    (instead of 'inserts')