Java heap space (java.lang.OutOfMemoryError)

In my project, I have a module to upload multiple image and create the thumbnails for it at once. For uploading, I am using JavaFX and for creating thumbnails, I am using Java.

I wrote upload code and call of thumbnail creation function inside a for loop. If the number of uploading images is more than five, I am getting this error:

Java heap space (java.lang.OutOfMemoryError)

I think, the code for uploading is fine, and the problem with thumbnail creation code. How can I solve this problem? How should I change the structure of my code ?

This is my JavaFX code:

fgUrl = fc.getSelectedFiles();
for(fg in fgUrl) {
    try {
        System.gc();
        fileURL = "file:///{fg.toString()}";
        fileURL = fileURL.replace("\", "/");
        def dt = DateTime{}.instant;
        var datetime = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss:SSS").format(dt);
        pic_url = datetime.replace("-", "_").replace(":", "_").replace(" ", "_");
        datetime = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(dt);
        f = new File("C:\uploaded\{pic_url}.jpg");
        uploadFile(fileURL, f,save_index,datetime,pic_url); // This function will save selected image in the working directory of the system.
        var resize_ob = new resizeImage(url.replace("file:///", ""),"C:/thumbnails/{pic_url2}.jpg");// This will call the java thumbnail creation function.
        save_index++;
    }
    catch(e:Exception) { }
}

Answer

You can try to use memory profilers to see which portion of code/class/method is consuming more memory. You can start with free JVisualVM or JConsole which comes with JDK.

Other well known profilers are:

-> Optimize IT

-> JProfiler