I am new to java and really need help!!!!

I need to create a:

1. class triangle with a method to find the area of a triangle using three sides, only if they form a valid triangle.Otherwise display a message "Triangle cannot be formed".

2. class shapes having three functions with my the same name findArea(), but difference in arguments list to find area of circle, square and rectangle.

3. class to compute the profit or loss percentage based on the cost price and selling price of an item.

Thank You,

Regards Matt.

I need these for my java project. PS:im only 13 yrs old .

Please Help.