Upgrade Regex with a tester() method?

[Peter Levart]

On 01/22/2013 09:29 AM, Paul Sandoz wrote:
> On Jan 21, 2013, at 6:20 PM, Peter Levart <peter.levart at gmail.com> wrote:
>> Another possible point lambdafication is an idiom that is frequent with using pattern matching - replacement:
>>
>> public class Pattern { ...
>>
>>     public String replaceAll(String str, Function<String, String> replacementFunction) {
>>         Matcher m = matcher(str);
>>         StringBuffer sb = new StringBuffer();
>>         while (m.find()) {
>>             m.appendReplacement(sb, replacementFunction.apply(m.group(1)));
>>         }
>>         m.appendTail(sb);
>>         return sb.toString();
>>     }
>>
>> so one can write:
>>
>>         Pattern pattern = Pattern.compile("\\{(.*?)\\}");
>>         String msg = pattern.replaceAll(
>>             "User's home is: {user.home}, current dir is: {user.dir}",
>> System::getProperty
>> );
>>
> Perhaps those function-based methods would be more appropriate on Matcher as overloads of replaceAll and replaceFirst?
>
> Paul.

That's better Paul, yes, since there is already 
Matcher.replaceAll(String replacement). I would also change the function 
to take the Matcher instance as the parameter instead of matched group 
#1 - more flexible:

public class Matcher { ...

     public String replaceAll(Function<Matcher, String> 
replacementFunction) {
         reset();
         boolean result = find();
         if (result) {
             StringBuffer sb = new StringBuffer();
             do {
                 appendReplacement(sb, replacementFunction.apply(this));
                 result = find();
             } while (result);
             appendTail(sb);
             return sb.toString();
         }
         return text.toString();
     }

So the above usage becomes:

     Pattern pattern = Pattern.compile("\\{(.*?)\\}");

     String msg = pattern
         .matcher("User's home is: {user.home}, current dir is: {user.dir}")
         .replaceAll(m -> System.getProperty(m.group(1)));



Regards, Peter

>
>> This method could then also be overloaded on String as a shortcut without precompiled Pattern instance:
>>
>> public class String {...
>>
>>     public String replaceAll(String regex, Function<String, String> replacementFunction) {
>>         return Pattern.compile(regex).replaceAll(this, replacementFunction);
>>     }
>>
>> so one could write:
>>
>>     String msg = "User's home is: {user.home}, current dir is: {user.dir}"
>>                      .replaceAll("\\{(.*?)\\}", System::getProperty);
>>