清理 ManagedProcess::getPid() (#2660)

* Delete getPID0

* Delete blank line

HMCLCore/src/main/java/org/jackhuang/hmcl/util/platform/ManagedProcess.java

@@ -17,12 +17,12 @@
  */
 package org.jackhuang.hmcl.util.platform;
 
-import net.burningtnt.bcigenerator.api.BytecodeImpl;
-import net.burningtnt.bcigenerator.api.BytecodeImplError;
 import org.jackhuang.hmcl.launch.StreamPump;
 import org.jackhuang.hmcl.util.Lang;
 
 import java.io.IOException;
+import java.lang.invoke.MethodHandles;
+import java.lang.invoke.MethodType;
 import java.lang.reflect.Field;
 import java.util.*;
 import java.util.function.Consumer;
@@ -92,7 +92,13 @@ public class ManagedProcess {
     public long getPID() throws UnsupportedOperationException {
         if (JavaVersion.CURRENT_JAVA.getParsedVersion() >= 9) {
             // Method Process.pid() is provided (Java 9 or later). Invoke it to get the pid.
-            return getPID0(process);
+            try {
+                return (long) MethodHandles.publicLookup()
+                        .findVirtual(Process.class, "pid", MethodType.methodType(long.class))
+                        .invokeExact(process);
+            } catch (Throwable e) {
+                throw new UnsupportedOperationException("Cannot get the pid", e);
+            }
         } else {
             // Method Process.pid() is not provided. (Java 8).
             if (OperatingSystem.CURRENT_OS == OperatingSystem.WINDOWS) {
@@ -118,23 +124,6 @@ public class ManagedProcess {
         }
     }
 
-    /**
-     * Get the PID of a process with BytecodeImplGenerator
-     */
-    @BytecodeImpl({
-            "LABEL METHOD_HEAD",
-            "ALOAD 0",
-            "INVOKEVIRTUAL Ljava/lang/Process;pid()J",
-            "LABEL RELEASE_PARAMETER",
-            "LRETURN",
-            "LOCALVARIABLE process [Ljava/lang/Process; METHOD_HEAD RELEASE_PARAMETER 0",
-            "MAXS 2 1"
-    })
-    @SuppressWarnings("unused")
-    private static long getPID0(Process process) {
-        throw new BytecodeImplError();
-    }
-
     /**
      * The command line.
      *