On and On and On $-$ Recursive Solution

Given an integer input, write a static recursive method called sum$()$ which returns create a sum of each integer between zero $(0)$ and the value of input.

For example: If the value of input is $6,$ the method should return the value of $6+5+4+3+2+1+0$ or $21$

Write a recursive method sum$()$ that calls itself and takes in the value stored in the variable input.

Base Case: There are two base cases.

if input is equal to zero $(0)$ or one $(1),$ return input;

Otherwise, return the value of input added to a recursive call to sum$(),$ passing in the next integer to be added. IN JAVA