Function overloading (or method overloading) in Java allows a class to have more than one method with the same name, provided their parameter lists are different. It helps to increase the readability of the program.

Key Points:

1. Method Name: Must be the same.
2. Parameter List: Must differ (either in the number of parameters, their types, or both).
3. Return Type: Can be the same or different, but it alone is not enough to distinguish between overloaded methods.
4. Access Modifiers: Can be different.

Constructor overloading in Java allows a class to have more than one constructor with different parameter lists. This enables the creation of objects in different ways.

Key Points:

1. Constructor Name: Must be the same as the class name.
2. Parameter List: Must differ (either in the number of parameters, their types, or both).
3. Purpose: To initialize objects in different ways.