I am developing a RCP application where I want to add a button which look like apple os button. I want this look in windows7. Is this possible ?
Yes it is possible, but as the commenters have mentioned, definitely not recommended. SWT will not support this out of the box, as it is designed to have native looking widgets on whatever platform it is running on.
Swing, on the other hand, supports many different types of "look and feel", since it is designed to look the same on whatever platform you are running on. It won't be perfect (since again, it's not the native widget), but it's easier than writing your own widget.
Your options are:
Keep in mind that with both of these solutions, your button will very quickly look out of date on newer versions of the OS if the native rendering of the button has changed.