Javaコードを実行する

JavaLauncher.java

import module java.desktop;

void main() {
    var f = new JFrame("Javaランチャー");
    f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    f.setSize(800, 600);
    f.setLocationRelativeTo(null);
    
    var split = new JSplitPane(JSplitPane.VERTICAL_SPLIT);
    var taSource = new JTextArea();
    taSource.setLineWrap(false);
    taSource.setFont(new Font(Font.MONOSPACED, Font.PLAIN, 12));
    split.add(JSplitPane.TOP, new JScrollPane(taSource, 
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED));
    var taLog = new JTextArea();
    taSource.setLineWrap(true);
    split.add(JSplitPane.BOTTOM, new JScrollPane(taLog, 
            JScrollPane.VERTICAL_SCROLLBAR_ALWAYS, JScrollPane.HORIZONTAL_SCROLLBAR_NEVER));
    f.add(split);
    var button = new JButton("起動");
    button.addActionListener(_ -> {
        taLog.setText("");
        Thread.ofPlatform().start(() -> launch(taSource.getText(), taLog));
    
    });
    var clip = new JButton("ログコピー");
    clip.addActionListener(_ -> copyToClipboard(taLog.getText()));
    var p = new JPanel(new FlowLayout(FlowLayout.RIGHT));
    p.add(button);
    p.add(clip);
    f.add(BorderLayout.SOUTH, p);
    
    f.setVisible(true);
    split.setDividerLocation(split.getHeight() * 2 / 3);
}

void copyToClipboard(String log) {
    StringSelection sel = new StringSelection(log);
    Toolkit.getDefaultToolkit()
           .getSystemClipboard()
           .setContents(sel, null);
}

final String JAVA_COMMAND = "path-to-jdk/bin/java.exe";

void launch(String source, JTextArea logArea) {
    Path tempFile = null;
    Path tempDIr = null;
    try {
        // "main.java"というファイル名でテンポラリディレクトリに一時保存
        tempDIr = Files.createTempDirectory("compileTmp");
        tempFile = tempDIr.resolve("main.java");

        Files.writeString(tempFile, source, StandardOpenOption.CREATE);
        // コンパイルしてエラーメッセージを表示
        Process process = new ProcessBuilder(JAVA_COMMAND, tempFile.toString())
                .redirectErrorStream(true)
                
                .start();

            try (BufferedReader br =
                    new BufferedReader(new InputStreamReader(process.getInputStream(), StandardCharsets.UTF_8))) {
                String line;
                boolean first = true;
                while ((line = br.readLine()) != null) {
                    if (first && line.startsWith("Picked up")) { first = false; continue;}
                    //一時フォルダ名部分を削除
                    String l = line.replace(tempDIr.toString() + "\\", "");;
                    SwingUtilities.invokeLater(() -> logArea.append(l + "\n"));
                }
            }        
        
        process.waitFor();
        if (process.exitValue() == 0) {
            logArea.append("no error\n");
            return;
        }
    } catch (Exception ex) {
        System.out.println(ex);
    } finally {
        // 一時ファイルを削除
        if (tempFile != null) {
            try {
                Files.deleteIfExists(tempFile);
            } catch (IOException _) {

            }
        }
        // 一時ディレクトリを削除
        if (tempDIr != null) {
            try {
                Files.deleteIfExists(tempDIr);
            } catch (IOException _) {
                // ignore cleanup failure
            }
        }
    }        
}