[core] Make Smack.getNoticeStream() more robust

Appearently simply calling ClassLoader.getSystemResourceAsStream()
works on Java SE but not on Android. But our FileUtils are able to
load the resource stream on Android.

smack-core/src/main/java/org/jivesoftware/smack/Smack.java

@@ -1,6 +1,6 @@
 /**
  *
- * Copyright 2020 Florian Schmaus
+ * Copyright 2020-2021 Florian Schmaus
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -19,6 +19,8 @@ package org.jivesoftware.smack;
 import java.io.InputStream;
 import java.util.logging.Logger;
 
+import org.jivesoftware.smack.util.FileUtils;
+
 public class Smack {
 
     private static final Logger LOGGER = Logger.getLogger(Smack.class.getName());
@@ -38,8 +40,20 @@ public class Smack {
 
     private static final String NOTICE_RESOURCE = SMACK_PACKAGE + "/NOTICE";
 
+    /**
+     * Get the stream of the NOTICE file of Smack.
+     * <p>
+     * This license of Smack requires that the contents of this NOTICE text file are shown "…within a display generated by
+     * the Derivative Works, if and wherever such third-party notices normally appear.".
+     * </p>
+     *
+     * @return the stream of the NOTICE file of Smack.
+     * @since 4.4.0
+     */
     public static InputStream getNoticeStream() {
-        return ClassLoader.getSystemResourceAsStream(NOTICE_RESOURCE);
+        InputStream res = FileUtils.getInputStreamForClasspathFile(NOTICE_RESOURCE);
+        assert res != null;
+        return res;
     }
 
     public static void ensureInitialized() {

smack-core/src/main/java/org/jivesoftware/smack/util/FileUtils.java

@@ -41,6 +41,19 @@ public final class FileUtils {
 
     private static final Logger LOGGER = Logger.getLogger(FileUtils.class.getName());
 
+    public static InputStream getInputStreamForClasspathFile(String path) {
+        return getInputStreamForClasspathFile(path, null);
+    }
+
+    public static InputStream getInputStreamForClasspathFile(String path, ClassLoader loader) {
+        try {
+            return getStreamForClasspathFile(path, loader);
+        } catch (IOException e) {
+            LOGGER.log(Level.FINE, "Suppressed IOException in getInputStreamForClasspathFile", e);
+            return null;
+        }
+    }
+
     public static InputStream getStreamForClasspathFile(String path, ClassLoader loader) throws IOException {
         // Get an array of class loaders to try loading the providers files from.
         List<ClassLoader> classLoaders = getClassLoaders();