What Issues prevent Java applications from working on multiple platforms?

Question

Java is supposed to be \"write once, run anywhere\" and it really can be, but in some cases it turns into \"write once, debug everywhere\".

What are the most common

Answer 1

Using classes from the com.sun.* packages that come with the Sun JDK.

Answer 2

Few from UI area:

• Incorrect ordering of buttons like OK/Cancel
• Using absolute layouts
• Different accelerator keys
• Different sizes/rendering of fonts
• Expecing certain keys to be present (Windows key, Meta key)

(These are not Java specific though)