handle basic argument substitution in MessageFormat.format

Thanks to Remi for an initial version of this patch.

classpath/java/text/MessageFormat.java

@@ -28,8 +28,14 @@ public class MessageFormat extends Format {
   public StringBuffer format(Object[] args, StringBuffer target,
                              FieldPosition p)
   {
-    // todo
+    // todo: handle other format substitutions and escapes, and make
-    return target.append(pattern);
+    // this more efficient:
+    String result = pattern;
+    int length = args.length;
+    for (int i = 0; i < length; i++) {
+      result = result.replace("{" + i + "}", String.valueOf(args[i]));
+    }
+    return target.append(result);
   }
 
   public StringBuffer format(Object args, StringBuffer target, FieldPosition p)

test/Strings.java

@@ -139,5 +139,12 @@ public class Strings {
 
     testDecode(false);
     testDecode(true);
+
+    expect
+      (java.text.MessageFormat.format
+       ("{0} enjoy {1} {2}.  do {4}?  {4} do?",
+        "I", "grape", "nuts", "foobar",
+        new Object() { public String toString() { return "you"; } })
+       .equals("I enjoy grape nuts.  do you?  you do?"));
   }
 }