Performance problem for loading large files (>3MB) - and a fix about jsyntaxpane HOT 2 OPEN

Another fix would be to override the read() method of DefaultEditorKit from

    public void read(Reader in, Document doc, int pos)
        throws IOException, BadLocationException {

        char[] buff = new char[4096];

to use higher block values

    public void read(Reader in, Document doc, int pos)
        throws IOException, BadLocationException {

        char[] buff = new char[409600];

Fixed in 
https://github.com/nordfalk/jsyntaxpane/commit/ad57ec63c99644ee492cb52ecada62868
58aadfd by simply not using the read() method of DefaultEditorKit