Java Image ASCII Converter

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.*;
import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Objects;

class Main {

    private final static String DEFAULT_ORIGINAL_IMAGE_PATH = "images/google.png";
    private final static String DEFAULT_ASCII_IMAGE_PATH = "images/copy.txt";

    public static void main(String[] args) {

        BufferedImage image = null;
        Color color;
        PrintWriter pw = null;

        try {
            image = ImageIO.read(new File(DEFAULT_ORIGINAL_IMAGE_PATH));
            pw = new PrintWriter(new File(DEFAULT_ASCII_IMAGE_PATH));
        } catch (IOException | NullPointerException e) {
            System.out.println(e.getMessage());
        }

        try {
            for (int i = 0; i < image.getHeight(); i++) {
                for (int j = 0; j < image.getWidth(); j++) {
                    color = new Color(image.getRGB(j, i));
                    double colorValue = ((double) color.getRed() + (double) color.getBlue() + (double) color.getGreen()) / 3;
                    Objects.requireNonNull(pw).append(getCharRepresentation(colorValue));
                }
            }
        } catch (NullPointerException npe) {
            System.out.println(npe.getMessage());
        }
    }

    private static char getCharRepresentation(double value) {
        if (value >= 230.0) {
            return ' ';
        } else if (value >= 200.0) {
            return '.';
        } else if (value >= 180.0) {
            return '*';
        } else if (value >= 160.0) {
            return ':';
        } else if (value >= 130.0) {
            return 'o';
        } else if (value >= 100.0) {
            return '&';
        } else if (value >= 70.0) {
            return '8';
        } else if (value >= 50.0) {
            return '#';
        } else {
            return '@';
        }
    }
}