Saida em JTextArea

import java.awt.Color;
import java.awt.Container;
import java.awt.GridLayout;
import java.io.IOException;
import java.net.InetAddress;
import java.util.ArrayList;
import java.util.List;

import javax.swing.JFrame;
import javax.swing.JTextArea;

public class IP extends JFrame {
	private static final long serialVersionUID = -3698253747230767087L;

	private final JTextArea textArea;
	private final List<String> listIP;
	
	public IP(final List<String> listIP) {
		this.listIP = listIP;
		textArea = new JTextArea();
		textArea.setBackground(Color.BLACK);
		textArea.setForeground(Color.GREEN);
		
		final Container container = getContentPane();
		container.setLayout(new GridLayout(1,1));
		container.add(textArea);
		
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setSize(350, 400);
		setResizable(false);
		setLocationRelativeTo(null);
		setVisible(true);
	}
	
	public void startPing() {
		for (final String host : listIP) {
			ping(host);
		}
	}
	
	private void ping(final String host) {
		try {
			if (InetAddress.getByName(host).isReachable(3000)) {
				textArea.append("SUCESSO: " + host + "\n");
			} else {
				textArea.append("FALHA: " + host + "\n");
			}
		} catch (final IOException e) {
			textArea.append("ERRO\n");
		}
	}

	public static void main(String[] args) {
		final List<String> listIP = new ArrayList<String>();
		listIP.add("10.1.1.2");
		listIP.add("10.13.101.77");
		listIP.add("10.13.101.64");
		listIP.add("10.1.1.2");
		listIP.add("10.13.101.77");
		listIP.add("10.13.101.64");
		
		IP app = new IP(listIP);
		app.startPing();
	}
}

jtextarea.append("texto");
jtextarea.setCaretPosition(jtextarea.getText().length());