[JENKINS-42934] Some unit tests need side-effects of FileInputStream

core/src/test/java/hudson/UtilTest.java

@@ -24,10 +24,6 @@
  */
 package hudson;
 
-import java.nio.channels.FileChannel;
-import java.nio.channels.FileLock;
-import java.nio.file.Files;
-import java.nio.file.StandardOpenOption;
 import java.util.List;
 import java.util.Map;
 import java.util.HashMap;
@@ -492,15 +488,15 @@ public class UtilTest {
         // On unix, can't use "chmod a-w" on the dir as the code-under-test undoes that.
         // On unix, can't use "chattr +i" because that needs root.
         // On unix, can't use "chattr +u" because ext fs ignores it.
+        // On Windows, can't use FileChannel.lock() because that doesn't block deletion
         // On Windows, we can't delete files that are open for reading, so we use that.
+        // NOTE: This is a hack in any case as there is no guarantee that all Windows filesystems
+        // will enforce blocking deletion on open files... just that the ones we normally
+        // test with seem to block.
         assert Functions.isWindows();
-        final FileChannel channel = FileChannel.open(f.toPath(), StandardOpenOption.READ, StandardOpenOption.WRITE);
-        final FileLock lock = channel.lock();
+        final InputStream s = new FileInputStream(f); // intentional use of FileInputStream
         unlockFileCallables.put(f, new Callable<Void>() {
-            public Void call() throws IOException {
-                lock.release();
-                channel.close();
-                return null; };
+            public Void call() throws IOException { s.close(); return null; };
         });
     }