java Character, String, ... classes

Character wrapper class contains useful methods for working with characters.

String immutable 0 or more characters.

java.util.StringBuilder (as of Java 5) and java.util.StringBuffer (slower than StringBuilder because it's synchronized) used for dynamically building or modifying strings.

java.util.regex.Pattern and java.util.regex.Matcher used for regular expression matching. java.util.StringTokenizer is earlier class to break strings into "tokens".

CharSequence is basic character interface.