--- old/src/share/classes/java/net/URLConnection.java	2020-06-26 21:42:19.098054226 +0100
+++ new/src/share/classes/java/net/URLConnection.java	2020-06-26 21:42:19.002053015 +0100
@@ -285,12 +285,7 @@
    /**
     * @since   JDK1.1
     */
-    private static FileNameMap fileNameMap;
-
-    /**
-     * @since 1.2.2
-     */
-    private static boolean fileNameMapLoaded = false;
+    private static volatile FileNameMap fileNameMap;
 
     /**
      * Loads filename map (a mimetable) from a data file. It will
@@ -302,18 +297,21 @@
      * @since 1.2
      * @see #setFileNameMap(java.net.FileNameMap)
      */
-    public static synchronized FileNameMap getFileNameMap() {
-        if ((fileNameMap == null) && !fileNameMapLoaded) {
-            fileNameMap = sun.net.www.MimeTable.loadTable();
-            fileNameMapLoaded = true;
+    public static FileNameMap getFileNameMap() {
+        FileNameMap map = fileNameMap;
+
+        if (map == null) {
+            fileNameMap = map = new FileNameMap() {
+                private FileNameMap internalMap =
+                    sun.net.www.MimeTable.loadTable();
+
+                public String getContentTypeFor(String fileName) {
+                    return internalMap.getContentTypeFor(fileName);
+                }
+            };
         }
 
-        return new FileNameMap() {
-            private FileNameMap map = fileNameMap;
-            public String getContentTypeFor(String fileName) {
-                return map.getContentTypeFor(fileName);
-            }
-        };
+        return map;
     }
 
     /**
--- old/src/share/classes/sun/nio/fs/AbstractFileTypeDetector.java	2020-06-26 21:42:19.483059086 +0100
+++ new/src/share/classes/sun/nio/fs/AbstractFileTypeDetector.java	2020-06-26 21:42:19.389057899 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -25,6 +25,8 @@
 
 package sun.nio.fs;
 
+import java.net.FileNameMap;
+import java.net.URLConnection;
 import java.nio.file.Path;
 import java.nio.file.spi.FileTypeDetector;
 import java.util.Locale;
@@ -50,6 +52,16 @@
         if (file == null)
             throw new NullPointerException("'file' is null");
         String result = implProbeContentType(file);
+
+        // Fall back to content types property.
+        if (result == null) {
+            Path fileName = file.getFileName();
+            if (fileName != null) {
+                FileNameMap fileNameMap = URLConnection.getFileNameMap();
+                result = fileNameMap.getContentTypeFor(fileName.toString());
+            }
+        }
+
         return (result == null) ? null : parse(result);
     }
 
--- old/test/java/nio/file/Files/probeContentType/Basic.java	2020-06-26 21:42:19.867063931 +0100
+++ new/test/java/nio/file/Files/probeContentType/Basic.java	2020-06-26 21:42:19.772062733 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2008, 2016, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -22,21 +22,24 @@
  */
 
 /* @test
- * @bug 4313887
+ * @bug 4313887 8146215
  * @summary Unit test for probeContentType method
  * @library ../..
  * @build Basic SimpleFileTypeDetector
  * @run main/othervm Basic
  */
 
-import java.nio.file.*;
 import java.io.*;
+import java.nio.file.*;
+import java.util.stream.Stream;
 
 /**
- * Uses Files.probeContentType to probe html file and custom file type.
+ * Uses Files.probeContentType to probe html file, custom file type, and minimal
+ * set of file extension to content type mappings.
  */
-
 public class Basic {
+    private static final boolean IS_UNIX =
+        ! System.getProperty("os.name").startsWith("Windows");
 
     static Path createHtmlFile() throws IOException {
         Path file = Files.createTempFile("foo", ".html");
@@ -51,7 +54,49 @@
         return Files.createTempFile("red", ".grape");
     }
 
+    private static void checkMimeTypesFile(Path mimeTypes) {
+        if (!Files.exists(mimeTypes)) {
+            System.out.println(mimeTypes + " does not exist");
+        } else if (!Files.isReadable(mimeTypes)) {
+            System.out.println(mimeTypes + " is not readable");
+        } else {
+            System.out.println(mimeTypes + " contents:");
+            try (Stream<String> lines = Files.lines(mimeTypes)) {
+                lines.forEach(System.out::println);
+                System.out.println("");
+            } catch (IOException ioe) {
+                System.err.printf("Problem reading %s: %s%n",
+                                  mimeTypes, ioe.getMessage());
+            }
+        }
+    }
+
+    private static int checkContentTypes(String expected, String actual) {
+        assert expected != null;
+        assert actual != null;
+
+        if (!expected.equals(actual)) {
+            if (IS_UNIX) {
+                Path userMimeTypes =
+                    Paths.get(System.getProperty("user.home"), ".mime.types");
+                checkMimeTypesFile(userMimeTypes);
+
+                Path etcMimeTypes = Paths.get("/etc/mime.types");
+                checkMimeTypesFile(etcMimeTypes);
+            }
+
+            System.err.println("Expected \"" + expected
+                               + "\" but obtained \""
+                               + actual + "\"");
+
+            return 1;
+        }
+
+        return 0;
+    }
+
     public static void main(String[] args) throws IOException {
+        int failures = 0;
 
         // exercise default file type detector
         Path file = createHtmlFile();
@@ -60,8 +105,7 @@
             if (type == null) {
                 System.err.println("Content type cannot be determined - test skipped");
             } else {
-                if (!type.equals("text/html"))
-                    throw new RuntimeException("Unexpected type: " + type);
+                failures += checkContentTypes("text/html", type);
             }
         } finally {
             Files.delete(file);
@@ -71,13 +115,18 @@
         file = createGrapeFile();
         try {
             String type = Files.probeContentType(file);
-            if (type == null)
-                throw new RuntimeException("Custom file type detector not installed?");
-            if (!type.equals("grape/unknown"))
-                throw new RuntimeException("Unexpected type: " + type);
+            if (type == null) {
+                System.err.println("Custom file type detector not installed?");
+                failures++;
+            } else {
+                failures += checkContentTypes("grape/unknown", type);
+            }
         } finally {
             Files.delete(file);
         }
 
+        if (failures > 0) {
+            throw new RuntimeException("Test failed!");
+        }
     }
 }