Java: java.util.StringTokenizer

Purpose

The java.util.StringTokenizer class is used to break strings into tokens (words, numbers, operators, or whatever). A more powerful solution is to use regular expressions, which have been added to Java 1.4.

A StringTokenizer constructor takes a string to break into tokens and returns a StringTokenizer object for that string. Each time its nextToken() method is called, it returns the next token in that string. If you don't specify the delimiters (separator characters), blanks are the default.

Constructors

StringTokenizer st = new StringTokenizer(s);: Creates a StringTokenizer for the String s that uses whitespace (blanks, tabs, newlines, returns, form feeds) as delimiters.
StringTokenizer st = new StringTokenizer(s, d);: Creates a StringTokenizer for the String s using delimiters from the String d.
StringTokenizer st = new StringTokenizer(s, d, f);: Creates a StringTokenizer for the String s using delimiters from the String d. If the boolean f is true, each delimiter character will also be returned as a token.

Common Methods

Assume that st is a StringTokenizer.

st.hasMoreTokens() -- Returns true if there are more tokens.
st.nextToken() -- Returns the next token as a String.
st.countTokens() -- Returns the int number of tokens. This can be used to allocate an array before starting, altho it can be inefficient for long strings because it has to scan the string once just to get this number. Using a Vector and converting it to an array at the end may be a better choice.

Example: Find the longest word in a String

This code finds the longest word (characters separated by delimiter characters) in the String s, using blanks, commas, and tabs as delimiters.

// Assume s contains a string of words
String longestWord = "";
StringTokenizer st = new StringTokenizer(s, " ,\t");
while (st.hasMoreTokens()) {
    String w = st.nextToken();
    if (w.length() > longestWord.length()) {
        longestWord = w;
    }
}