Terminal

package me.nrubin29.terminal;

import javax.swing.*;
import javax.swing.filechooser.FileSystemView;
import java.awt.*;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.io.BufferedReader;
import java.io.File;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;

public class Terminal extends JFrame {

    private JTextArea area;
    private File workingFolder;

    public Terminal() {
        area = new JTextArea();
        workingFolder = FileSystemView.getFileSystemView().getDefaultDirectory();
        setTitle("Terminal (" + workingFolder.getPath() + ")");

        area.addKeyListener(new KeyListener() {
            public void keyPressed(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_ENTER) {
                    try {
                        String command = area.getText().split("\n")[area.getLineOfOffset(area.getCaretPosition())];
                        if (command.equals("")) return;

                        Process p = new ProcessBuilder("bash", "-c", command).directory(workingFolder).start();

                        area.setEditable(false);

                        int code = p.waitFor();

                        writeStream(p.getErrorStream());
                        writeStream(p.getInputStream());

                        if (code == 0 && command.startsWith("cd") && command.split(" ").length >= 2) workingFolder = new File(command.split(" ")[1]);

                        Terminal.this.setTitle("Terminal (" + workingFolder.getPath() + ")");

                        area.setEditable(true);
                    }
                    catch (Exception ex) { error(ex); }
                }
                else if (e.getKeyCode() == KeyEvent.VK_DELETE) e.setSource(null);
            }
            public void keyTyped(KeyEvent e) { }
            public void keyReleased(KeyEvent e) { }
        });

        area.setBackground(Color.black);
        area.setForeground(Color.green);
        area.setCaretColor(Color.green);
        area.setFont(new Font(Font.MONOSPACED, Font.PLAIN, 12));

        JScrollPane pane = new JScrollPane(area);
        pane.setBorder(BorderFactory.createEmptyBorder());
        pane.setHorizontalScrollBarPolicy(JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED);
        pane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);

        add(pane);

        Dimension DIM = new Dimension(640, 480);
        setPreferredSize(DIM);
        setSize(DIM);
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLocationRelativeTo(null);
        setResizable(true);
        pack();
        setVisible(true);
    }

    public static void main(String[] args) {
        new Terminal();
    }

    private void write(String... lines) {
        area.append("\n");
        for (String line : lines) {
            area.append("\n" + line);
        }
    }

    private void error(Exception e) {
        write("An error has occured.", e.getMessage());
        e.printStackTrace();
    }

    private void writeStream(InputStream s) {
        try {
            BufferedReader reader = new BufferedReader(new InputStreamReader(s));

            ArrayList<String> strs = new ArrayList<String>();

            while(reader.ready()) strs.add(reader.readLine());

            write(strs.toArray(new String[strs.size()]));

            s.close();
        }
        catch (Exception e) { e.printStackTrace(); }
    }
}