"Exception in thread "AWT-EventQueue-0" java.lang.OutOfMemoryError: Java heap space"

Ok, so I have a problem that is giving me this error and I am hoping that there might be someone who could help me out.

Code:
    private String CalcFileSize(){
            System.out.println("Calculating Size of File");
            File _tempFile = new File (fileName.getText());
            System.out.print(_tempFile.length());
            byte [] _fileSizeGetter = new byte [(int)_tempFile.length()];
            _fileSizeToSend = _fileSizeGetter.length;
            String _sendFileSize = Integer.toString(_fileSizeToSend);
            System.out.println("File Size Calculated");
            return _sendFileSize;

    }
Ok, this function basically creates a File called _tempFile and loads something into it (for example, if fileName.getText() == "source.pdf" then it will grab that file and throw it into _tempFile). The problem occurs when I use a large file. Particularly something like a 200meg file. Anyone have a suggestion on a possible way around this?