String Formatter in GWT

Question

How do I format my string in GWT?

I made a method

  Formatter format = new Formatter();
    int matches = 0;
    Formatter formattedString = format.forma         


        

Answer 1

This one is pretty fast and ignores bad curly-delimited values:

public static String format(final String format, final Object... args)
{
    if (format == null || format.isEmpty()) return "";

    // Approximate the result length: format string + 16 character args
    StringBuilder sb = new StringBuilder(format.length() + (args.length*16));

    final char openDelim = '{';
    final char closeDelim = '}';

    int cur = 0;
    int len = format.length();
    int open;
    int close;

    while (cur < len)
    {
        switch (open = format.indexOf(openDelim, cur))
        {
            case -1:
                return sb.append(format.substring(cur, len)).toString();

            default:
                sb.append(format.substring(cur, open));
                switch (close = format.indexOf(closeDelim, open))
                {
                    case -1:
                        return sb.append(format.substring(open)).toString();

                    default:
                        String nStr = format.substring(open + 1, close);
                        try
                        {
                            // Append the corresponding argument value
                            sb.append(args[Integer.parseInt(nStr)]);
                        }
                        catch (Exception e)
                        {
                            // Append the curlies and the original delimited value
                            sb.append(openDelim).append(nStr).append(closeDelim);
                        }
                        cur = close + 1;
                }
        }
    }

    return sb.toString();
}

Answer 2

Or even simpler, not using RegExp, and using only Strings:

public static String format(final String format, final String... args) {
    String[] split = format.split("%s");
    final StringBuffer msg = new StringBuffer();
    for (int pos = 0; pos < split.length - 1; pos += 1) {
        msg.append(split[pos]);
        msg.append(args[pos]);
    }
    msg.append(split[split.length - 1]);
    return msg.toString();
 }

Answer 3

As mentionned above, there is GWT formatters for numbers and dates : NumberFormat and DateTimeFormat. Still, I needed a solution for the well-know String.format(...) case. I end up with this solution, I don't know if it's wrong for performance, but it's visually clean. I'd be glad to hear any comment on it, or about other solution.

My String formatter :

public class Strings {

    public static String format(final String format, final Object... args) {
        String retVal = format;
        for (final Object current : args) {
            retVal = retVal.replaceFirst("[%][s]", current.toString());
        }
        return retVal;
    }

}

and the JUTest if one want to re-use this :

public class StringsTest {

    @Test
    public final void testFormat() {
        this.assertFormat("Some test here  %s.", 54);
        this.assertFormat("Some test here %s and there %s, and test [%s].  sfsfs !!!", 54, 59, "HAHA");

    }

    private void assertFormat(final String format, final Object... args) {
        Assert.assertEquals("Formatting is not working", String.format(format, args), Strings.format(format, args));
    }

}

Answer 4

I'm not keen on abusing string manipulation for doing regexps' job, but, based on bodrin's solution, you can code:

public static String format (String pattern, final Object ... args) {
    for (Object arg : args) {
        String part1 = pattern.substring(0,pattern.indexOf('{'));
        String part2 = pattern.substring(pattern.indexOf('}') + 1);
        pattern = part1 + arg + part2;
    }   
    return pattern;
}

Answer 5

A very simple replacement for String.format() in GWT 2.1+:

import com.google.gwt.regexp.shared.RegExp;
import com.google.gwt.regexp.shared.SplitResult;

public static String format(final String format, final Object... args) {
  final RegExp regex = RegExp.compile("%[a-z]");
  final SplitResult split = regex.split(format);
  final StringBuffer msg = new StringBuffer();
  for (int pos = 0; pos < split.length() - 1; ++pos) {
    msg.append(split.get(pos));
    msg.append(args[pos].toString());
  }
  msg.append(split.get(split.length() - 1));
  return msg.toString();
}

Answer 6

An extension to Daniels solution: Also supports escaping using ' and throws if a number cannot be parsed (like the JVM version does):

private static final char OPEN = '{';
private static final char CLOSE = '}';
private static final char ESCAPE = '\'';

@Override
public String format(String pattern, Object... arguments) {
    if (pattern == null || pattern.isEmpty())
        return "";

    // Approximate the result length: format string + 16 character args
    StringBuilder sb = new StringBuilder(pattern.length() + (arguments.length * 16));

    int cur = 0;
    int len = pattern.length();
    // if escaped, then its >= 0
    int escapedAtIndex = -1;

    while (cur < len) {
        char currentChar = pattern.charAt(cur);
        switch (currentChar) {
            case OPEN:
                if (escapedAtIndex >= 0) {
                    // currently escaped
                    sb.append(currentChar);
                } else {
                    // find close
                    int close = pattern.indexOf(CLOSE, cur + 1);
                    switch (close) {
                        case -1:
                            // Missing close. Actually an error. But just ignore
                            sb.append(currentChar);
                            break;
                        default:
                            // Ok, we have a close
                            final String nStr = pattern.substring(cur + 1, close);
                            try {
                                // Append the corresponding argument value
                                sb.append(arguments[Integer.parseInt(nStr)]);
                            } catch (Exception e) {
                                if (e instanceof NumberFormatException) {
                                    throw new IllegalArgumentException(nStr +
                                            " is not a number.");
                                }
                                // Append the curlies and the original delimited value
                                sb.append(OPEN).append(nStr).append(CLOSE);
                            }
                            // Continue after the close
                            cur = close;
                            break;
                    }
                }
                cur++;
                break;
            case ESCAPE:
                // Special case: two '' are just converted to '
                boolean nextIsEscapeToo = (cur + 1 < len) && pattern.charAt(cur + 1) == ESCAPE;
                if (nextIsEscapeToo) {
                    sb.append(ESCAPE);
                    cur = cur + 2;
                } else {
                    if (escapedAtIndex >= 0) {
                        // Escape end.
                        escapedAtIndex = -1;
                    } else {
                        // Escape start.
                        escapedAtIndex = cur;
                    }
                    cur++;
                }
                break;
            default:
                // 90% case: Nothing special, just a normal character
                sb.append(currentChar);
                cur++;
                break;
        }
    }
    return sb.toString();
}

This implementation and the JVM-Version both pass those tests:

    // Replace: 0 items
    assertFormat("Nothing to replace", "Nothing to replace");
    // Replace: 1 item
    assertFormat("{0} apples", "15 apples", 15);
    assertFormat("number of apples: {0}", "number of apples: zero", "zero");
    assertFormat("you ate {0} apples", "you ate some apples", "some");
    // Replace 2 items
    assertFormat("{1} text {0}", "second text first", "first", "second");
    assertFormat("X {1} text {0}", "X second text first", "first", "second");
    assertFormat("{0} text {1} X", "first text second X", "first", "second");

Escaping-Tests:

    // Escaping with no replacement
    assertFormat("It's the world", "Its the world");
    assertFormat("It''s the world", "It's the world");
    assertFormat("Open ' and now a second ' (closes)", "Open  and now a second  (closes)");
    assertFormat("It'''s the world", "It's the world");
    assertFormat("'{0}' {1} {2}", "{0} one two", "zero", "one", "two");
    // Stays escaped (if end escape is missing)
    assertFormat("'{0} {1} {2}", "{0} {1} {2}", "zero", "one", "two");
    assertFormat("'{0} {1}' {2}", "{0} {1} two", "zero", "one", "two");
    // No matter where we escape, stays escaped
    assertFormat("It's a {0} world", "Its a {0} world", "blue");
    // But we can end escape everywhere
    assertFormat("It's a {0} world, but not '{1}",
            "Its a {0} world, but not always", "blue", "always");
    // I think we want this
    assertFormat("It''s a {0} world, but not {1}",
            "It's a blue world, but not always", "blue", "always");
    // Triple
    assertFormat("' '' '", " ' ");
    // From oracle docs
    assertFormat("'{''}'", "{'}");
    // Missing argument (just stays 0)
    assertFormat("begin {0} end", "begin {0} end");
    // Throws
    try {
        assertFormat("begin {not_a_number} end", "begin {not_a_number} end");
        throw new AssertionError("Should not get here");
    } catch (IllegalArgumentException iae) {
        // OK
    }