Question

My question is similar to this question, which asks how to substitute properties into a string such as

Transfer {0} from {1} to {2} on {3}

The answer to that question, the MessageFormat class, won’t work with my needs. I’d like to substitute named parameteres into a string like:

The {weather} in {location} stays mainly in the {terrain}.

or perhaps

The ${weather} in ${location} stays mainly in the ${terrain}.

Am I lucky enough that there already exists a class like MessageFormat to help with that or should I cobble together something on my own to do it? Ant does this with build.xml – but short of lifting their code I’m wondering if there is already an existing class.

Answer 1

May I suggest creating a new class called CustomMessageFormat:

public class CustomMessageFormat
{
    public static String format( String message, Object[] params )
    {
        Pattern pattern = Pattern.compile( "\\{(.*?)\\}" );
        Matcher matcher = pattern.matcher( message );
        StringBuffer sb = new StringBuffer();
        int i = 0;
        while ( matcher.find() )
        {
            matcher.appendReplacement( sb, "{" + ( i++ ) + "}" );
        }
        matcher.appendTail( sb );

        return MessageFormat.format( sb.toString(), params );
    }
}

That all that does is replace all your {sometext} tokens with sequential ones ({1}, {2} etc.) as required by MessageFormat.format method.

The you can simply use:

public static void main( String[] args )
{
    String inputMessage = "The {def1} in {def2} stays mainly in the {def3}.";
    String result = CustomMessageFormat.format( inputMessage, new Object[] { "sun", "Paris", "suburbs" } );
    System.out.println( result );
}

This is, of course, a rough example, but I hope you get the idea.