How To Check if a String has All Unique Characters?

Hi, I’m Bhargav Kaneria. I live in Pune, India. By profession I am a young software
developer(Trainee). I like to learn new languages(obviously programming!). I’m comfortable in Java. I also have some knowledge of Ruby, Groovy and a bit of JavaScript(learning currently) and a bit of PHP. My area of interests include programming(duh!), Internet, data structures and algorithms, economics and history(mostly related to world war II).