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PlantUML is a component that allows to quickly write diagrams from text.
There is a newer version: 1.2024.8
// THIS FILE HAS BEEN GENERATED BY A PREPROCESSOR.
package net.sourceforge.plantuml.dot;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

import net.sourceforge.plantuml.OptionFlags;
import net.sourceforge.plantuml.api.MyRunnable;
import net.sourceforge.plantuml.api.TimeoutExecutor;
import net.sourceforge.plantuml.log.Logme;
import net.sourceforge.plantuml.security.SFile;

public class ProcessRunner {
	// ::remove file when __CORE__

	private final String[] cmd;

	private String error;
	private String out;

	private volatile ProcessState state = ProcessState.INIT();
	private final Lock changeState = new ReentrantLock();

	public ProcessRunner(String[] cmd) {
		this.cmd = cmd;
	}

	public ProcessState run(byte in[], OutputStream redirection) {
		return run(in, redirection, null);
	}

	public ProcessState run(byte in[], OutputStream redirection, SFile dir) {
		if (this.state.differs(ProcessState.INIT())) {
			throw new IllegalStateException();
		}
		this.state = ProcessState.RUNNING();
		final MainThread mainThread = new MainThread(cmd, dir, redirection, in);
		try {
			// http://steveliles.github.io/invoking_processes_from_java.html
			final long timeoutMs = OptionFlags.getInstance().getTimeoutMs();
			final boolean done = new TimeoutExecutor(timeoutMs).executeNow(mainThread);
		} finally {
			changeState.lock();
			try {
				if (state.equals(ProcessState.RUNNING())) {
					state = ProcessState.TIMEOUT();
					// mainThread.cancel();
				}
			} finally {
				changeState.unlock();
			}
		}
		if (state.equals(ProcessState.TERMINATED_OK())) {
			assert mainThread != null;
			this.error = mainThread.getError();
			this.out = mainThread.getOut();
		}
		return state;
	}

	class MainThread implements MyRunnable {

		private final String[] cmd;
		private final SFile dir;
		private final OutputStream redirection;
		private final byte[] in;
		private volatile Process process;
		private volatile ThreadStream errorStream;
		private volatile ThreadStream outStream;

		public MainThread(String[] cmd, SFile dir, OutputStream redirection, byte[] in) {
			this.cmd = cmd;
			this.dir = dir;
			this.redirection = redirection;
			this.in = in;
		}

		public String getOut() {
			return outStream.getString();
		}

		public String getError() {
			return errorStream.getString();
		}

		public void runJob() throws InterruptedException {
			try {
				startThreads();
				if (state.equals(ProcessState.RUNNING())) {
					final int result = joinInternal();
				}
			} finally {
				changeState.lock();
				try {
					if (state.equals(ProcessState.RUNNING())) {
						state = ProcessState.TERMINATED_OK();
					}
				} finally {
					changeState.unlock();
				}
				if (process != null) {
					process.destroy();
					close(process.getErrorStream());
					close(process.getOutputStream());
					close(process.getInputStream());
				}
			}

		}

		public void cancelJob() {
			// The changeState lock is ok
			// assert changeState.tryLock();
			// assert state == ProcessState.TIMEOUT;
			if (process != null) {
				errorStream.cancel();
				outStream.cancel();
				process.destroy();
				// interrupt();
				close(process.getErrorStream());
				close(process.getOutputStream());
				close(process.getInputStream());
			}
		}

		private void startThreads() {
			try {
				process = Runtime.getRuntime().exec(cmd, null, dir == null ? null : dir.conv());
			} catch (IOException e) {
				Logme.error(e);
				changeState.lock();
				try {
					state = ProcessState.IO_EXCEPTION1(e);
				} finally {
					changeState.unlock();
				}
				Logme.error(e);
				return;
			}
			errorStream = new ThreadStream(process.getErrorStream(), null);
			outStream = new ThreadStream(process.getInputStream(), redirection);
			errorStream.start();
			outStream.start();
			if (in != null) {
				final OutputStream os = process.getOutputStream();
				try {
					try {
						os.write(in);
					} finally {
						os.close();
					}
				} catch (IOException e) {
					changeState.lock();
					try {
						state = ProcessState.IO_EXCEPTION2(e);
					} finally {
						changeState.unlock();
					}
					Logme.error(e);
				}
			}
		}

		public int joinInternal() throws InterruptedException {
			errorStream.join();
			outStream.join();
			final int result = process.waitFor();
			return result;
		}

	}

	class ThreadStream extends Thread {

		private volatile InputStream streamToRead;
		private volatile OutputStream redirection;
		private volatile StringBuffer sb = new StringBuffer();

		ThreadStream(InputStream streamToRead, OutputStream redirection) {
			this.streamToRead = streamToRead;
			this.redirection = redirection;
		}

		public String getString() {
			if (sb == null) {
				return "";
			}
			return sb.toString();
		}

		public void cancel() {
			assert state.equals(ProcessState.TIMEOUT()) || state.equals(ProcessState.RUNNING()) : state;
			this.interrupt();
			sb = null;
			streamToRead = null;
			redirection = null;
			// Because of this, some NPE may occurs in run() method, but we do not care
		}

		@Override
		public void run() {
			int read = 0;
			try {
				while ((read = streamToRead.read()) != -1) {
					if (state.equals(ProcessState.TIMEOUT())) {
						return;
					}
					if (redirection == null) {
						sb.append((char) read);
					} else {
						redirection.write(read);
					}
				}
			} catch (Throwable e) {
				System.err.println("ProcessRunnerA " + e);
				Logme.error(e);
				sb.append('\n');
				sb.append(e.toString());
			}
		}
	}

	public final String getError() {
		return error;
	}

	public final String getOut() {
		return out;
	}

	private void close(InputStream is) {
		try {
			if (is != null) {
				is.close();
			}
		} catch (IOException e) {
			Logme.error(e);
		}
	}

	private void close(OutputStream os) {
		try {
			if (os != null) {
				os.close();
			}
		} catch (IOException e) {
			Logme.error(e);
		}
	}

}