Reducing time complexcity in java

Question

I have developed one application which recursively iterates through all Documents version in parent node (DOM) .
and lists report in outfile .
For each version found i am creating one collection object and at end itrating all objects , outputting it to file .
     // Create Doc iterator
         while (allDocfinish) {
                   check for version of each Doc
                     while (All Version Finishes) {
                             // Read version collect File information .
                            // Add information to Collection (Each object is Java Bean )
      // Iterator Collection Obj
         // OutPut it to CSV I am currently following this format . but this is taking too much time . It is not throwing any Out Of Memory exception
But it is running for more than 20 hours to get all node information (near abt 150 nodes each having 50 - 70 versions in it )
Please suggest solution how do i optimize this
Thanks
Amit

Answer 1

ejp wrote:
That's only 10,500 operations.It's not many. You can't reduce the time complexity of M*N if you have to visit them all. You can loop to 10,500 in much less than a second. So I'd suggest your problems lie elsewhere, most probably in String concatenation when you should be using a StringBuffer or StringBuilder.I am reading whole file version each time to calculate file size . (Putting this in string Buffer Using StringWriter for this )
Even if there is string operation , for each iteration same string references are assigned with new object .