In Java: Assume the availability of an existing class, ICalculator, that models an integer arithmetic calculator and contains:

a private instance variable currentValue that stores the current int value of the calculator
a getter method for the above instance variable
methods add, sub, mul, and div
Each method in ICalculator receives an int argument and applies its operation to currentValueand returns the new value of currentValue. So, if currentValue has the value 8 and sub(6) is invoked then currentValue ends up with the value 2, and 2 is returned.

Write a public subclass, ICalculator1, based on ICalculator. The class ICalculator1 has one additional method, sign, that receives no arguments, and doesn't modify currentValue. Instead, it simply returns 1, 0 or -1 depending on whether currentValue is positive, zero, or negative respectively.