URL url = new URL(stringUrl);
    BufferedImage bimg = ImageIO.read(url);
    ByteArrayOutputStream bas = new ByteArrayOutputStream();
    ImageIO.write(bimg, "png", bas);
    byte[] buffer = bas.toByteArray();

 Como estou usando....

public static String imagemToStringByUrlWeb(String stringUrl) throws Exception{
    System.out.println("URL QUE ESTA SENDO LIDO: "+stringUrl);
    byte[] b = Base64Coder.imagemToByteArrayByUrlWeb(stringUrl);
    ByteBuffer bb = ByteBuffer.wrap(b);
    String s = Base64Coder.encodeLines(bb.array());
    System.out.println(s.length()+" kb");
    return s;
}

public static byte[] imagemToByteArrayByUrlWeb(String stringUrl) throws Exception{
    System.out.println("URL QUE ESTA SENDO LIDO: "+stringUrl);
    URL url = new URL(stringUrl);
    BufferedImage bimg = ImageIO.read(url);
    ByteArrayOutputStream bas = new ByteArrayOutputStream();
    ImageIO.write(bimg, "png", bas);
    byte[] buffer = bas.toByteArray();
    return buffer;
}

Download do JDom

package xmlparse;

import java.io.StringReader;
import java.util.Iterator;
import java.util.List;
import org.jdom.CDATA;
import org.jdom.Comment;

import org.jdom.Document;
import org.jdom.Element;
import org.jdom.EntityRef;
import org.jdom.ProcessingInstruction;
import org.jdom.Text;
import org.jdom.input.SAXBuilder;

/**
 *
 * @author raydacosta
 */
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer();
        sb.append("<blog>");
        sb.append("  <author>");
        sb.append("    <name>Guilherme Silveira</name>");
        sb.append("  </author>");
        sb.append("  <entries>");
        sb.append("    <entry>");
        sb.append("      <title>first</title>");
        sb.append("      <description>My first blog entry.</description>");
        sb.append("    </entry>");
        sb.append("    <entry>");
        sb.append("      <title>tutorial</title>");
        sb.append("      <description>");
        sb.append("        Today we have developed a nice alias tutorial. Tell your friends! NOW!");
        sb.append("      </description>");
        sb.append("    </entry>");
        sb.append("  </entries>");
        sb.append("</blog>");

        Document doc = readDocument(sb.toString());
        List children = doc.getContent();
        listNodes(doc, 0);


    }


private static Document readDocument(String xml) {
        try {
          SAXBuilder builder = new SAXBuilder();
          Document result = builder.build(new StringReader(xml));
          return result;
        } catch(Exception e) {
          e.printStackTrace();
        }
        return null;
}


public static void listNodes(Object o, int depth) {
   if (o instanceof Element) {
      Element element = (Element) o;
      System.out.println("Element: " + element.getName());
      List children = element.getContent();
      Iterator iterator = children.iterator();
      while (iterator.hasNext()) {
        Object child = iterator.next();
        listNodes(child, depth+1);
      }
   }else if (o instanceof Document) {
      System.out.println("Document");
      Document doc = (Document) o;
      List children = doc.getContent();
      Iterator iterator = children.iterator();
      while (iterator.hasNext()) {
        Object child = iterator.next();
        listNodes(child, depth+1);
      }
   }else if (o instanceof Comment) {
      System.out.println("Comment");
   }else if (o instanceof CDATA) {
      System.out.println("CDATA section");
      // CDATA is a subclass of Text so this test must come
      // before the test for Text.
   }else if (o instanceof Text) {
       Text txt = ((Text)o);
      System.out.println("Valor: "+txt.getTextTrim());
   }else if (o instanceof EntityRef) {
      System.out.println("Entity reference");
   }else if (o instanceof ProcessingInstruction) {
      System.out.println("Processing Instruction");
   }else {  // This really shouldn't happen
      System.out.println("Unexpected type: " + o.getClass());
   }

  }

  private static void printSpaces(int n) {
    for (int i = 0; i < n; i++) {
      System.out.print(' ');
    }

  }

}