In MetalFileChooserUI.java, the following line exists.
    newFolderAccessibleName =
        UIManager.getString("FileChooser.newFolderAccessibleName",l);
However, a key named "newFolderAccessibleName" isn't contained in metal*.properties. Instead, "nameFolderAccessibleNam" exists.
Is "...Nam" misspelling of "...Name"? If so, it should be corrected.

And also, each localized metal_xx.properties file also contains a key named "newFolderAccessibleNam" not "newFolderAccessibleName".
It should be corrected.