Download Stuff From Reddit Using Java

import java.io.*;
import java.net.URL;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.charset.Charset;
import java.nio.file.*;
import java.util.Arrays;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

public class getWallpaper {
    private static final String OPEN_SUBREDDIT = "http://www.reddit.com/r/%s/.json";

    public static String readAll(Reader rd) throws IOException {
        StringBuilder sb = new StringBuilder();
        int cp;
        while ((cp = rd.read()) != -1) {
            sb.append((char) cp);
        }
        return sb.toString();
    }

    public static JSONObject subredditJson(String subreddit) throws IOException, JSONException {
        InputStream is = new URL(String.format(OPEN_SUBREDDIT, subreddit)).openStream();
        try {
            BufferedReader rd = new BufferedReader(new InputStreamReader(is, Charset.forName("UTF-8")));
            String jsonText = readAll(rd);
            JSONObject json = new JSONObject(jsonText);
            return json;
        } finally {
            is.close();
        }
    }

    static void wallpaperLinks(JSONObject json) {
        String[] wallpapers;
        JSONArray data = json.getJSONObject("data").getJSONArray("children"); 
        // the children is where the information is contained

        for (int i = 0; i < data.length(); i++) {
            // iterate over JSONArray, and extract url
            JSONObject urlInfo = data.getJSONObject(i);
            String wallpaper = urlInfo.getJSONObject("data").getString("url");
            if (wallpaper.substring(wallpaper.length() - 4, wallpaper.length()).equals(".jpg")) {
                String[] fileName = wallpaper.split("/");
                try {
                    downloadFile(wallpaper, String.format("%s.jpg", fileName[fileName.length - 1]));
                } catch (IOException e) {
                    System.out.println("File not found");
                }
            }
        }
    }

    static void downloadFile(String url, String target) throws IOException {
        URL urlFile = new URL(url);
        ReadableByteChannel rbc = Channels.newChannel(urlFile.openStream());
        FileOutputStream fos = new FileOutputStream(target);
        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
    }

    public static void main(String[] args) throws IOException, JSONException {
        JSONObject json = subredditJson("EarthPorn");
        wallpaperLinks(json);
    }
}