Simplify ParentProcessWatcher

See eclipse-lemminx/lemminx#1753

Signed-off-by: David Thompson <davthomp@redhat.com>

Author: datho7561

qute.ls/com.redhat.qute.ls/src/main/java/com/redhat/qute/ls/commons/ParentProcessWatcher.java

@@ -13,20 +13,17 @@
 *******************************************************************************/
 package com.redhat.qute.ls.commons;
 
-import java.io.IOException;
+import java.util.Optional;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
 import java.util.function.Function;
-import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import org.eclipse.lsp4j.jsonrpc.MessageConsumer;
 import org.eclipse.lsp4j.services.LanguageServer;
 
-import com.google.common.io.Closeables;
-
 /**
  * Watches the parent process PID and invokes exit if it is no longer available.
  * This implementation waits for periods of inactivity to start querying the
@@ -86,58 +83,8 @@ private boolean parentProcessStillRunning() {
 		if (pid == 0 || lastActivityTime > (System.currentTimeMillis() - INACTIVITY_DELAY_SECS)) {
 			return true;
 		}
-		String command;
-		if (isWindows) {
-			command = "cmd /c \"tasklist /FI \"PID eq " + pid + "\" | findstr " + pid + "\"";
-		} else {
-			command = "kill -0 " + pid;
-		}
-		Process process = null;
-		boolean finished = false;
-		try {
-			process = Runtime.getRuntime().exec(command);
-			finished = process.waitFor(POLL_DELAY_SECS, TimeUnit.SECONDS);
-			if (!finished) {
-				process.destroy();
-				finished = process.waitFor(POLL_DELAY_SECS, TimeUnit.SECONDS); // wait for the process to stop
-			}
-			if (isWindows && finished && process.exitValue() > 1) {
-				// the tasklist command should return 0 (parent process exists) or 1 (parent
-				// process doesn't exist)
-				LOGGER.warning("The tasklist command: '" + command + "' returns " + process.exitValue());
-				return true;
-			}
-			return !finished || process.exitValue() == 0;
-		} catch (IOException | InterruptedException e) {
-			LOGGER.log(Level.WARNING, e.getMessage(), e);
-			return true;
-		} finally {
-			if (process != null) {
-				if (!finished) {
-					process.destroyForcibly();
-				}
-				// Terminating or destroying the Process doesn't close the process handle on
-				// Windows.
-				// It is only closed when the Process object is garbage collected (in its
-				// finalize() method).
-				// On Windows, when the Java LS is idle, we need to explicitly request a GC,
-				// to prevent an accumulation of zombie processes, as finalize() will be called.
-				if (isWindows) {
-					// Java >= 9 doesn't close the handle when the process is garbage collected
-					// We need to close the opened streams
-					if (!isJava1x) {
-						Closeables.closeQuietly(process.getInputStream());
-						Closeables.closeQuietly(process.getErrorStream());
-						try {
-							Closeables.close(process.getOutputStream(), false);
-						} catch (IOException e) {
-						}
-					}
-					System.gc();
-				}
-			}
-		}
-
+		Optional<ProcessHandle> optionalHandle = ProcessHandle.of(pid);
+		return optionalHandle.isPresent() && optionalHandle.get().isAlive();
 	}
 
 	@Override