FULL PRODUCT VERSION :
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
java version "9.0.4"
Java(TM) SE Runtime Environment (build 9.0.4+11)
Java HotSpot(TM) 64-Bit Server VM (build 9.0.4+11, mixed mode)

A DESCRIPTION OF THE PROBLEM :
If directory "x" exists, attempting to change to it in JFileChooser by entering text in the "File Name:" field and hitting enter will fail with an InvalidPathException if "x " (actual filename with a space added) is accidentally entered.

Note that in Java 8, the file chooser will strip the trailing whitespace and change to the "x" directory, which is also probably the wrong thing to do, but not nearly as bad as an unexpected and not-easily-catchable runtime exception.

REGRESSION. Last worked in version 8u162

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run code from directory with write permissions.

Enter "testspace " (without the quotes) in the "File Name:" field of the file chooser and hit "Enter".

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Expect the file chooser to close (accept "testspace " as a file name different from the "testspace" directory).

ACTUAL -
An InvalidPathException is thrown.

ERROR MESSAGES/STACK TRACES THAT OCCUR :
Exception in thread "AWT-EventQueue-0" java.nio.file.InvalidPathException: Trailing char < > at index 62: C:\Users\larry\Documents\jgrasp\jgrasp_world.205\tmp\testspace
at java.base/sun.nio.fs.WindowsPathParser.normalize(WindowsPathParser.java:191)
at java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:153)
at java.base/sun.nio.fs.WindowsPathParser.parse(WindowsPathParser.java:77)
at java.base/sun.nio.fs.WindowsPath.parse(WindowsPath.java:92)
at java.base/sun.nio.fs.WindowsFileSystem.getPath(WindowsFileSystem.java:229)
at java.base/java.nio.file.Paths.get(Paths.java:84)
at java.desktop/sun.awt.shell.ShellFolder.getShellFolder(ShellFolder.java:247)
at java.desktop/javax.swing.plaf.basic.BasicFileChooserUI.changeDirectory(BasicFileChooserUI.java:1352)
at java.desktop/javax.swing.plaf.basic.BasicFileChooserUI.access$000(BasicFileChooserUI.java:50)
at java.desktop/javax.swing.plaf.basic.BasicFileChooserUI$ApproveSelectionAction.actionPerformed(BasicFileChooserUI.java:1141)
at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:269)
at java.desktop/java.awt.AWTEventMulticaster.mouseReleased(AWTEventMulticaster.java:297)
at java.desktop/java.awt.Component.processMouseEvent(Component.java:6578)
at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3343)
at java.desktop/java.awt.Component.processEvent(Component.java:6343)
at java.desktop/java.awt.Container.processEvent(Container.java:2259)
at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:4961)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2317)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4793)
at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4904)
at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4539)
at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4480)
at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2303)
at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2758)
at java.desktop/java.awt.Component.dispatchEvent(Component.java:4793)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:766)
at java.desktop/java.awt.EventQueue.access$500(EventQueue.java:97)
at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:717)
at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:711)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:89)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:99)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:739)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:737)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:89)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:736)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:199)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:117)
at java.desktop/java.awt.WaitDispatchSupport$2.run(WaitDispatchSupport.java:190)
at java.desktop/java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:235)
at java.desktop/java.awt.WaitDispatchSupport$4.run(WaitDispatchSupport.java:233)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.desktop/java.awt.WaitDispatchSupport.enter(WaitDispatchSupport.java:233)
at java.desktop/java.awt.Dialog.show(Dialog.java:1070)
at java.desktop/javax.swing.JFileChooser.showDialog(JFileChooser.java:756)
at java.desktop/javax.swing.JFileChooser.showSaveDialog(JFileChooser.java:678)
at JFileChooserBug18$1.run(JFileChooserBug18.java:13)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:313)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:764)
at java.desktop/java.awt.EventQueue.access$500(EventQueue.java:97)
at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:717)
at java.desktop/java.awt.EventQueue$3.run(EventQueue.java:711)
at java.base/java.security.AccessController.doPrivileged(Native Method)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:89)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:734)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:199)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:124)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:109)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:90)


REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import javax.swing.*;
import java.io.File;

public class JFileChooserBug18 {
   public static void main(String args[]) {
      SwingUtilities.invokeLater(
         new Runnable() {
            public void run() {
               File f = new File("testspace");
               f.mkdir();
               JFileChooser fc = new JFileChooser();
               fc.setCurrentDirectory(f.getAbsoluteFile().getParentFile());
               fc.showSaveDialog(null);
            }
         });
   }
}


---------- END SOURCE ----------