RuntimeDemo

Die Klasse java.lang.Runtime besitzt die statische Methode getRuntime(), die das Java Runtime Environment zurückgibt. Mit dieser Referenz können wir externe Programme ausführen, indem wir die exec()-Methode der Klasse Runtime aufrufen.

/*
 * RuntimeDemo.java
 * The class java.lang.Runtime features a static method called getRuntime(), 
 * which retrieves the current Java Runtime Environment. 
 * With that reference, we can run external programs by invoking the Runtime class's exec() method.
 *
 */
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.logging.*;
import javax.swing.*;

public class RuntimeDemo {

    private JButton btRun;
    private JLabel lbCommand;
    private JTextArea textarea;
    private JTextField tfCommand;
    private JToolBar toolbar;

    public RuntimeDemo() {
        JFrame f = new JFrame("RuntimeDemo");
        f.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        toolbar = new JToolBar();
        lbCommand = new JLabel("Command: ");
        tfCommand = new JTextField();
        btRun = new JButton("Run");
        textarea = new JTextArea();
        toolbar.setRollover(true);
        toolbar.add(lbCommand);
        toolbar.add(tfCommand);
        btRun.setFocusable(false);
        btRun.addActionListener(new ActionListener() {

            @Override
            public void actionPerformed(final ActionEvent evt) {
                btRunActionPerformed(evt);
            }
        });
        toolbar.add(btRun);
        f.getContentPane().add(toolbar, BorderLayout.PAGE_START);
        f.getContentPane().add(new JScrollPane(textarea), BorderLayout.CENTER);
        f.setSize(800, 600);
        f.setLocationRelativeTo(null);
        f.setVisible(true);
    }

    private void btRunActionPerformed(final ActionEvent evt) {
        btRun.setEnabled(false);
        final String command = tfCommand.getText();
        SwingWorker worker = new SwingWorker() {

            @Override
            protected Object doInBackground() throws Exception {
                runCommand(command);
                return null;
            }

            @Override
            protected void done() {
                JOptionPane.showMessageDialog(RuntimeDemo.this.btRun, "Done");
                btRun.setEnabled(true);
            }
        };
        worker.execute();
    }

    private int runCommand(final String command) {
        int exitVal = -1;
        try {
            String osName = System.getProperty("os.name");
            String[] cmd = new String[3];
            Logger.getLogger("log").log(Level.INFO, osName);
            if (osName.equals("Windows XP") || osName.equals("Windows NT")) {
                cmd[0] = "cmd.exe";
                cmd[1] = "/C";
                cmd[2] = "\"" + command + "\"";
            } else {
                Logger.getLogger("log").log(Level.INFO, "os not supported");
            }
            Runtime rt = Runtime.getRuntime();
            Logger.getLogger("log").log(Level.INFO, "Execing {0} {1} {2}", new Object[]{cmd[0], cmd[1], cmd[2]});
            Process proc = rt.exec(cmd);
            // any error message?
            StreamGobbler errorGobbler = new StreamGobbler(proc.getErrorStream(), "ERROR");
            // any output?
            StreamGobbler outputGobbler = new StreamGobbler(proc.getInputStream(), "OUTPUT");
            // kick them off
            errorGobbler.start();
            outputGobbler.start();
            // any error???
            exitVal = proc.waitFor();
            Logger.getLogger("log").log(Level.INFO, "ExitValue: {0}", exitVal);
        } catch (final Throwable t) {
            Logger.getLogger("log").log(Level.SEVERE, null, t);
            JOptionPane.showMessageDialog(RuntimeDemo.this.btRun, "Error");
            btRun.setEnabled(true);
        }
        return exitVal;
    }

    public static void main(final String[] args) {
        Runnable gui = new Runnable() {

            @Override
            public void run() {
                RuntimeDemo runtimeDemo = new RuntimeDemo();
            }
        };
        //GUI must start on EventDispatchThread:
        EventQueue.invokeLater(gui);
    }

    private class StreamGobbler extends Thread {

        private InputStream is;
        private String type;
        private OutputStream os;

        StreamGobbler(final InputStream is, final String type) {
            this(is, type, null);
        }

        StreamGobbler(final InputStream is, final String type, final OutputStream redirect) {
            this.is = is;
            this.type = type;
            this.os = redirect;
        }

        @Override
        public void run() {
            try {
                PrintWriter pw = null;
                if (os != null) {
                    pw = new PrintWriter(os);
                }
                InputStreamReader isr = new InputStreamReader(is);
                BufferedReader br = new BufferedReader(isr);
                String line = null;
                line = br.readLine();
                while (line != null) {
                    if (pw != null) {
                        pw.println(line);
                    }
                    final String lineOut = line;
                    textarea.append(type + ">" + lineOut + "\n");
                    line = br.readLine();
                }
                if (pw != null) {
                    pw.flush();
                }
            } catch (final IOException ioe) {
                Logger.getLogger("log").log(Level.SEVERE, null, ioe);
            }
        }
    }
}

Viele externe Programme lassen sich aber heute deutlich komfortabler mit Hilfe der Klasse {{JAPI|Desktop}} ausführen.