java - Why isn't this multithreaded code faster? -

this java code. before, calls batchgenerateresult sequentially lengthy process, want try multithreading , have each 1 of them run @ same time. when test it, new time same old time. expected new time faster. know whats wrong?

public class plutomake {    public static string classdir;    public static void main(string[] args) throws jsonexception, ioexception,       interruptedexception {      // determine path class file, use current directory     string classdirfile = plutomake.class.getresource("plutomake.class")         .getpath();     classdir = classdirfile.substring(0, classdirfile.lastindexof("/") + 1);      // input arguments     final string logopath;     final string filename;     if (args.length < 2) {       logopath = classdir + "tests/android.png";       filename = "result.png";     } else {       logopath = args[0];       filename = args[1];     }      // make sure logo image exists     file logofile = new file(logopath);     if (!logofile.exists() || logofile.isdirectory()) {       system.exit(1);     }      // master.js file     string text = readfile(classdir + "master.js");     jsonarray files = new jsonarray(text);      executorservice es = executors.newcachedthreadpool();      // loop through active templates     int len = files.length();     (int = 0; < len; += 1) {       final jsonobject template = files.getjsonobject(i);       if (template.getboolean("active")) {         es.execute(new runnable() {           @override           public void run() {             try {               batchgenerateresult(logopath, template.getstring("template"),                   template.getstring("mapping"),                   template.getstring("metadata"), template.getstring("result")                       + filename, template.getstring("filter"),                   template.getstring("mask"), template.getint("x"),                   template.getint("y"), template.getint("w"),                   template.getint("h"));             } catch (ioexception | jsonexception e) {               // todo auto-generated catch block               e.printstacktrace();             }           }         });       }     }      es.shutdown();     boolean finshed = es.awaittermination(2, timeunit.minutes);   }    private static void batchgenerateresult(string logopath, string templatepath,       string mappingpath, string metadatapath, string resultpath,       string filter, string maskpath, int x, int y, int w, int h)       throws ioexception, jsonexception {     colorfilter filterobj = null;     if (filter.equals("none")) {       filterobj = new nofilter();     } else if (filter.equals("darken")) {       filterobj = new darken();     } else if (filter.equals("vividlight")) {       filterobj = new vividlight();     } else {       system.exit(1);     }      string text = readfile(classdir + metadatapath);     jsonobject metadata = new jsonobject(text);      map<point, point> mapping = myjson.readmapping(classdir + mappingpath);      bufferedimage warpedimage = exporter.generatewarpedlogo(logopath, maskpath,         mapping, metadata.getint("width"), metadata.getint("height"));     // imageio.write(warpedimage, "png", new fileoutputstream(classdir +     // "warpedlogo.png"));      exporter.stamplogo(templatepath, resultpath, x, y, w, h, warpedimage,         filterobj);      warpedimage.flush();   }    private static string readfile(string path) throws ioexception {     file file = new file(path);     fileinputstream fis = new fileinputstream(file);     byte[] data = new byte[(int) file.length()];     fis.read(data);     fis.close();     string text = new string(data, "utf-8");     return text;   } } 

it looks like, practical purposes following code should 1 can improve performance using multithreading.

bufferedimage warpedimage = exporter.generatewarpedlogo(logopath, maskpath,     mapping, metadata.getint("width"), metadata.getint("height")); // imageio.write(warpedimage, "png", new fileoutputstream(classdir + // "warpedlogo.png"));  exporter.stamplogo(templatepath, resultpath, x, y, w, h, warpedimage,     filterobj); 

the rest of major io - doubt how performance improvement can achieve there.

do profile , check how long each 1 of methods executing. depending on should able understand.