Andy Andy - 7 months ago 20
Java Question

Named placeholders in string formatting

In Python, when formatting string, I can fill placeholders by name rather than by position, like that:

print "There's an incorrect value '%(value)s' in column # %(column)d" % \
{ 'value': x, 'column': y }


I wonder if that is possible in Java (hopefully, without external libraries)? Thanks in advance.

Answer

Thanks for all your help! Using all your clues, I've written routine to do exactly what I want -- python-like string formatting using dictionary. Since I'm Java newbie, any hints are appreciated.

public static String dictFormat(String format, Hashtable<String, Object> values) {
    StringBuilder convFormat = new StringBuilder(format);
    Enumeration<String> keys = values.keys();
    ArrayList valueList = new ArrayList();
    int currentPos = 1;
    while (keys.hasMoreElements()) {
        String key = keys.nextElement(),
        formatKey = "%(" + key + ")",
        formatPos = "%" + Integer.toString(currentPos) + "$";
        int index = -1;
        while ((index = convFormat.indexOf(formatKey, index)) != -1) {
            convFormat.replace(index, index + formatKey.length(), formatPos);
            index += formatPos.length();
        }
        valueList.add(values.get(key));
        ++currentPos;
    }
    return String.format(convFormat.toString(), valueList.toArray());
}