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did you change your displayInterest methods?
Replace that InterestCalculator7 with just "object".
like object.getPincipal()
Replace all in this methods and it should work.

Also I think there is something wrong with you interest calculator. When you enter 25000 in principal amount and 15% APR, the interest paid is way too much. That doesnt happen in real world.

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I see you have already passed the information to the InterestCalculator7 class. Simply write a getter method in the InterestCalculator7 class. user object to call those data.

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you...

By studying your program I see that there are lots of things you didn't do quite well.
When you display you information, you are not displaying any data there, rather you are asking the user to...