I am currently developing a java application whose GUI slightly differs with respect to OS.
The screenshots of the app in WINDOWS 7 and Redhat linux is as follows


As we can see from the pictures, the consistency of GUI elements differs. How can I make the GUI consistent?
Thanks in advance.
Use a platform-consistent
look and feelfor your application.See:
http://docs.oracle.com/javase/tutorial/uiswing/lookandfeel/plaf.html
Nimbus is a recent one that looks decent:
http://docs.oracle.com/javase/tutorial/uiswing/lookandfeel/nimbus.html