Use Process's pid() when it exists.

(Done via reflection so it also works for java versions < 9)
Else fall back to old reflective method.

src/com/sheepit/client/os/windows/WinProcess.java

@@ -21,6 +21,7 @@ package com.sheepit.client.os.windows;
 
 import java.io.IOException;
 import java.lang.reflect.Field;
+import java.lang.reflect.InvocationTargetException;
 import java.util.ArrayList;
 import java.util.List;
 
@@ -61,35 +62,71 @@ public class WinProcess {
 		}
 	}
 	
-	public WinProcess(Process process) {
-		this();
+	private static boolean processHasGetPid() {
 		try {
-			Field f = process.getClass().getDeclaredField("handle");
-			f.setAccessible(true);
-			long val = f.getLong(process);
-			this.handle = new WinNT.HANDLE();
-			this.handle.setPointer(Pointer.createConstant(val));
-			this.pid = Kernel32.INSTANCE.GetProcessId(this.handle);
+			if (Process.class.getMethod("pid", null) != null) {
+				return true;
+			}
 		}
-		catch (NoSuchFieldException e) {
-		}
-		catch (IllegalArgumentException e) {
-		}
-		catch (IllegalAccessException e) {
+		catch (NoSuchMethodException | SecurityException e) {
 		}
+		return false;
 	}
 	
-	public WinProcess(int pid_) throws IOException {
-		this();
-		this.handle = Kernel32.INSTANCE.OpenProcess(0x0400 | // PROCESS_QUERY_INFORMATION
+	private static long getPid(Process process) {
+		try {
+			return (long) Process.class.getMethod("pid", null).invoke(process, null);
+		}
+		catch (IllegalAccessException | IllegalArgumentException | InvocationTargetException | NoSuchMethodException | SecurityException e) {
+		}
+		return 0;
+	}
+	
+	private static WinNT.HANDLE getHandleByPid(int pid_) throws IOException {
+		WinNT.HANDLE handle = Kernel32.INSTANCE.OpenProcess(0x0400 | // PROCESS_QUERY_INFORMATION
 				0x0800 | // PROCESS_SUSPEND_RESUME
 				0x0001 | // PROCESS_TERMINATE
 				0x0200 | // PROCESS_SET_INFORMATION
 				0x00100000, // SYNCHRONIZE
 				false, pid_);
-		if (this.handle == null) {
+		if (handle == null) {
 			throw new IOException("OpenProcess failed: " + Kernel32Util.formatMessageFromLastErrorCode(Kernel32.INSTANCE.GetLastError()) + " (pid: " + pid_ + ")");
 		}
+		return handle;
+	}
+	
+	public WinProcess(Process process) {
+		this();
+		if (processHasGetPid()) {
+			int _pid = (int) getPid(process);
+			try {
+				this.handle = getHandleByPid(_pid);
+			}
+			catch (IOException e) {
+			}
+			this.pid = _pid;
+		}
+		else {
+			try {
+				Field f = process.getClass().getDeclaredField("handle");
+				f.setAccessible(true);
+				long val = f.getLong(process);
+				this.handle = new WinNT.HANDLE();
+				this.handle.setPointer(Pointer.createConstant(val));
+				this.pid = Kernel32.INSTANCE.GetProcessId(this.handle);
+			}
+			catch (NoSuchFieldException e) {
+			}
+			catch (IllegalArgumentException e) {
+			}
+			catch (IllegalAccessException e) {
+			}
+		}
+	}
+	
+	public WinProcess(int pid_) throws IOException {
+		this();
+		this.handle = getHandleByPid(pid_);
 		this.pid = pid_;
 	}