StringTokenizer

StringTokenizer is a class in Java's `java.util` package used for breaking down a string into a sequence of tokens. It works by identifying delimiters, which are characters that separate the tokens. By default, StringTokenizer uses whitespace characters (space, tab, newline, carriage return, form feed) as delimiters.

To use StringTokenizer, you first create an instance by passing the string to be tokenized and optionally a string specifying the delimiter characters. For example, `StringTokenizer st = new StringTokenizer("this is a test");` will create a tokenizer for the sentence "this is a test" using default delimiters. If you wanted to split by commas, you would use `StringTokenizer st = new StringTokenizer("apple,banana,cherry", ",");`.

The class provides methods to retrieve tokens. `countTokens()` returns the number of tokens remaining. `hasMoreTokens()` checks if there are more tokens to be processed. The `nextToken()` method returns the next token in the sequence. Once a token is returned by `nextToken()`, it cannot be retrieved again.

StringTokenizer is a legacy class and is generally not recommended for new development. The `String.split()` method, which uses regular expressions for more powerful and flexible parsing, is preferred. However, StringTokenizer can still be encountered in older codebases. It is simpler to use than regular expressions for basic tokenization tasks but lacks their advanced features.