Activation functions. Write a program ActivationFunction.java to compute various activation functions that arise in neural networks. An activation function is a function that maps real numbers into a desired range, such as between $0$ and $1$ or between $1$ and $+1.$

The Heaviside step function is given by

H$($x$)=0121$if x$<0$if x$=0$if x$>0$