iPhone Dialpad-like dynamic phone number formatter.

phoneNumberFormatter.java

/**
* A semicolon separated list of formatting strings to format. "N"
* represents any single digit. [1-9()-] represents an exact digit. The
* underscore "_" represents a SPACE (not an underscore). These rules will
* be followed sequentially until one is matched.
*/
private static final String DIALPLAN = "+1_NNN_NNN_NNNN;1_(NNN)_NNN-NNNN;NNN-NNNN;(NNN)_NNN-NNNN";

/**
* Formats a phone number according to the rules defined in
* {@link #DIALPLAN}.
* 
* @param number
* the non-formatted number
* @param isPartialOk
* true if the number passed in "number" are just the first few
* digits of the formatted number. This might be the case on a
* dialpad where the number is being inputted right now
* @return
*/
public static String formatDialplanNumber(String number, boolean isPartialOk) {
    StringBuilder output = new StringBuilder(32);
    
    /*
    * k = index of "number" that we're trying to match d = index of
    * "DIALPLAN" that we're trying to match cd = character of "DIALPLAN" at
    * index "d" cn = character of "number" at index "k" ln = length of
    * "number" match = does it match so far
    */
    int k = 0;
    boolean match = true;
    int ln = number.length();
    for (int d = 0; d < DIALPLAN.length(); d++) {
    
        char cd = DIALPLAN.charAt(d);
        char cn = k < ln ? number.charAt(k) : 0;
        
        // move on to the next rule
        if (cd == ';') {
            if (match && k == ln)
                break;
            
            k = 0;
            match = true;
            if (output.length() > 0)
            output.delete(0, output.length());
            continue;
        }
        
        if (!match)
            continue;
        
        // next character in "number" must match exactly
        if (cd == '+' || cd == '#' || cd == '*' || cd >= '0' && cd <= '9') {
            if (k < ln && cn == cd) {
                output.append(cd);
                k++;
            }
            else {
                match = false;
            }
        }
        
        // next character in "number" must be a digit
        else if (cd == 'N') {
            if (k == ln) {
                if (isPartialOk)
                    output.append(' ');
                else
                    match = false;
            } else if (cn >= '0' && cn <= '9') {
                output.append(cn);
                k++;
            } else {
                match = false;
            }
        }
        
        // just add space to the output
        else if (cd == '_') {
            output.append(' ');
        }
        
        // just add the literal character to the output
        else if (cd == '(' || cd == ')' || cd == '-' || cd == '.') {
            output.append(cd);
        }
    }
    
    if (!match || k != ln) {
        // Didn't match anything... just rely on built-in phone number
        // formatter
        return PhoneNumberUtils.formatNumber(number);
    }
    
    // Remove non-numbers from the end of the string
    int end = output.length();
    
    int i = output.indexOf("( ");
    if (i > -1)
    end = i;
    
    while (end > 0 && (output.charAt(end - 1) == ' ' || output.charAt(end - 1) == '-')) {
        end--;
    }
    
    String formatted = output.substring(0, end);
    return formatted;
}