When I reformat code with Eclipse, it turns method headers like this:
public void myMethod(String param) {
into method headers like this:>
In my version of Eclipse, I found the option under Window->Preferences->Java->Code Style->Formatter, then clicked the Edit.. button.
In the new window, go to the Line Wrapping tab and find Method Declarations. You want to change the Line wrapping policy. The Force split check box seems to do the same.