Named placeholders in string formatting

Question

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 c         


        

Answer 1

You could have something like this on a string helper class

/**
 * An interpreter for strings with named placeholders.
 *
 * For example given the string "hello %(myName)" and the map 
 *      
Map map = new HashMap();
 *      
map.put("myName", "world");
 * 
 *
 * the call {@code format("hello %(myName)", map)} returns "hello world"
 *
 * It replaces every occurrence of a named placeholder with its given value
 * in the map. If there is a named place holder which is not found in the
 * map then the string will retain that placeholder. Likewise, if there is
 * an entry in the map that does not have its respective placeholder, it is
 * ignored.
 *
 * @param str
 *            string to format
 * @param values
 *            to replace
 * @return formatted string
 */
public static String format(String str, Map values) {

    StringBuilder builder = new StringBuilder(str);

    for (Entry entry : values.entrySet()) {

        int start;
        String pattern = "%(" + entry.getKey() + ")";
        String value = entry.getValue().toString();

        // Replace every occurence of %(key) with value
        while ((start = builder.indexOf(pattern)) != -1) {
            builder.replace(start, start + pattern.length(), value);
        }
    }

    return builder.toString();
}