Java is case-sensitive. There's a difference between "string" and String, and between "system" and "System". Capitalize those two words and you should be okay.
Java style suggests that class names be in the form MyClassName (first letter of each word in caps) and variable/method names in the form myMethodName (initial lowercase, internal capitalization). It's good to stick with that form, it makes your code easier to read. Especially useful if you're asking other to help you solve problems in your code.