please use java

Write and prove code. Write a block of code that calculates the smallest even number greater than or equal to x and stores it in y. In other words, y will be assigned either x or x+1. Assume x and y have already been initialized, and annotate your code with assertions before and after each statement to prove that it is correct. At the end of the block, it should be true that y is even and that y equals x or y equals x +1