How to use a regex to search backwards effectively?

Question

I\'m searching forward in an array of strings with a regex, like this:

for (int j = line; j < lines.length; j++) {  
    if (lines[j] == null || lines[j].         


        

Answer 1

I use the following simple class to search backwards in java

public class ReverseMatcher {
   private final Matcher _matcher;
   private final Stack _results = new Stack<>();

   public ReverseMatcher(Matcher matcher){
       _matcher = matcher;
   }

   public boolean find(){
       return find(_matcher.regionEnd());
   }

   public boolean find(int start){
       if (_results.size() > 0){
           _results.pop();
           return _results.size() > 0;
       }
       boolean res = false;
       while (_matcher.find()){            
           if (_matcher.end() > start)
               break;
           res = true;
           _results.push(_matcher.toMatchResult());
       }
       return res;
   }

   public String group(int group){
       return _results.peek().group(group);               
   }

   public String group(){
       return _results.peek().group();               
   }

   public int start(){
       return _results.peek().start();
   }    

   public int end(){
       return _results.peek().end();
   }
}

using:

String srcString = "1 2 3 4 5 6 7 8 9";
String pattern = "\\b[0-9]*\\b";
Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(srcString);
ReverseMatcher rm = new ReverseMatcher(m);
while (rm.find())
   System.out.print(rm.group() + " ");

output: 9 8 7 6 5 4 3 2 1

or

while (rm.find(9))
   System.out.print(rm.group() + " ");

output: 5 4 3 2 1