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I'm confused about why you needed a new print method. Wouldn't overriding putEmp() have done the trick?

First hit for googling "java overriding": Overriding and Hiding Methods (The Java™ Tutorials > Learning the Java Language > Interfaces and Inheritance)

I believe what you want to do is override the putEmp() method.

You seem to expect putTrade() to be called. But where do you call that?