Replacing characters in a string

I want to replace characters in a string using loops and if statements. For example if there is a Y in the string, I want to change it to a J. If there is an M in the string I want to change it to a Q.

[Ameer Hamza]

Why for loop? Why not some built-in function. This seems like a homework question. Can you show us the code you already tried?

[Patrick Crosby]

The way I was thinking of it would be using loops-- is there an easier way? I am unfamiliar with a built-in function for this

Answer 1

[Birdman]

One example(use regexprep):

s="Yao Ming";
regexprep(s,{'Y','M'},{'J','Q'})