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Eric2012 is spamming the forum.

What do the printlns outputs show you about the timing/sequencing of the events?
Add more printlns to show when the methods are called and the variables given values.

Is there more than one variable named oos? Do you give one a value and use the other one at the NPE?

This would be more direct: System.out.println("oos is " + oos);

You have several debugging...