xml - Java read a w3c.Document from different thread -

i'm trying read xml document multiple threads. documents large! program works if use sinlge thread if use worker thread errors. single thread takes 30-40 seconds load. multiple threads takes 5 seconds. advantage clear. can't work. if can shed light on i'd love know.

here code. not have (removed lot of comments , try-catch blocks , stuff doesn't relate problem)

        import org.w3c.dom.*;         import java.net.url;         private static documentbuilder getbuilder() {           try {             documentbuilderfactory dbfactory = documentbuilderfactory.newinstance();             return dbfactory.newdocumentbuilder();           } catch (parserconfigurationexception ex) {             string err = "error initializing api interface: \n" + ex.getmessage();             system.out.println(err);             joptionpane.showmessagedialog(null, err, "loading error", joptionpane.warning_message);             system.exit(1);           }           return null;         }         public void loadpage(string page) {           url url = new url(page);           document doc = getbuilder().parse(url.openstream());           element root = doc.getdocumentelement();           nodelist nodes = root.getchildnodes();           (int = 0; < nodes.getlength(); i++) {             node n = nodes.item(i);             if (n instanceof element) {               // move node new document.               document doc;               doc = getbuilder().newdocument();               node nn = doc.adoptnode(n);               doc.appendchild(nn);               element ele = (element)nn;               new parser(ele).start(); // causes errors...               //new parser(ele).run(); // works, isn't threaded.               nodelist nodes = root.getchildnodes();               = 0;             }           }         }         public class parser implements runnable {           private element ele;           public parser(element e) {             ele = e;           }           public void start() {             new thread(this).start();           }           @override           public void run() {             // parse document here.             // errors here if it's multi-threaded.           }         } 

edit:

the errors corrupted data. upon further testing i've discovered problem worse thought. function 'loadpage' above called thread. testing @ point posted question done 1 thread running. have found if run multiple page loads in parrelell (even thought different pages) errors if i'm using 1 thread per page...

my fear there static object being used somewhere causing state corruption , resulting in corrupted data.

an example of corrupted data this.

     // when reading xml      // <date>2015-6-1</date>       public string gettext(element ele) {         string val = ele.getfirstchild().getnodevalue();       }      // either empty string or somthing "13e13" or ".5d4" 

and multiple page loads mean following:

        public void loadall(list<string> pages) {           for(string page : pages) {             new loader(page).start();           }         }         public class loader implements runnable {           private string page;           public loader(string p) {             page = p;           }           public void start() {             new thread(this).start();           }           @override           public void run() {             loadpage(page);           }         } 

the dom not thread-safe. access needs synchronized, read-only access. that's because dom lazy evaluation, apparent read requests can trigger internal updates. it's pretty horrible. better off using xom or jdom2 if that's possible.