import java.awt.Toolkit;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import java.net.URL;

import javax.swing.JEditorPane;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTabbedPane;
import javax.swing.SwingUtilities;

public class HTMLDarstellenClass {

	private static final long serialVersionUID = 1L;

	private JEditorPane htmlPane, textPane;

	public HTMLDarstellenClass() {
		htmlPane = new JEditorPane();
		htmlPane.setContentType("text/html");
		JScrollPane htmlSP = new JScrollPane(htmlPane);
		textPane = new JEditorPane();
		textPane.setContentType("text/plain");
		JTabbedPane tabbedPane = new JTabbedPane();
		JScrollPane textSP = new JScrollPane(textPane);
		tabbedPane.add(htmlSP, "HTML");
		tabbedPane.add(textSP, "Quelltext");

		setURL();
        JFrame frame = new JFrame("HTML darstellen");
        frame.add(tabbedPane);
        frame.setSize(Toolkit.getDefaultToolkit().getScreenSize());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible(true);
	}

	private void setURL() {
		try {
			URL url = new URL("https://javabeginners.de");
			InputStream in = url.openStream();
			InputStreamReader isr = new InputStreamReader(in);
			StringBuffer buff = new StringBuffer();

			int len;
			while ((len = isr.read()) != -1) {
				buff.append((char) len);
			}
			in.close();
			isr.close();
			htmlPane.setPage(url);
			textPane.setText(buff.toString());
		} catch (MalformedURLException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public static void main(String[] args) {
		SwingUtilities.invokeLater(() -> new HTMLDarstellenClass());
	}
}