This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Your subject line and your message both seem to say different things, and I'm guessing what you're really asking is yet another, third thing: how to turn a single String into an array of char. That's an easy one -- the String class has a single method toCharArray() that does it: