Add a PathMatcher for CloudStorageFileSystem (#1469)

Add a test, as well.
We reuse the default PathMatcher since it does a fine job of globbing files.

google-cloud-contrib/google-cloud-nio/src/main/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystem.java

@@ -27,6 +27,7 @@
 import java.net.URISyntaxException;
 import java.nio.file.FileStore;
 import java.nio.file.FileSystem;
+import java.nio.file.FileSystems;
 import java.nio.file.Path;
 import java.nio.file.PathMatcher;
 import java.nio.file.WatchService;
@@ -210,13 +211,9 @@ public Set<String> supportedFileAttributeViews() {
     return SUPPORTED_VIEWS;
   }
 
-  /**
-   * Throws {@link UnsupportedOperationException} because this feature hasn't been implemented yet.
-   */
   @Override
   public PathMatcher getPathMatcher(String syntaxAndPattern) {
-    // TODO(#813): Implement me.
-    throw new UnsupportedOperationException();
+    return FileSystems.getDefault().getPathMatcher(syntaxAndPattern);
   }
 
   /**

google-cloud-contrib/google-cloud-nio/src/test/java/com/google/cloud/storage/contrib/nio/CloudStorageFileSystemTest.java

@@ -34,6 +34,7 @@
 import java.nio.file.FileSystems;
 import java.nio.file.Files;
 import java.nio.file.Path;
+import java.nio.file.PathMatcher;
 import java.nio.file.Paths;
 import java.util.ArrayList;
 import java.util.List;
@@ -159,4 +160,27 @@ public void testListFiles() throws IOException {
       assertThat(got).containsExactlyElementsIn(goodPaths);
     }
   }
+
+  @Test
+  public void testMatcher() throws IOException {
+    try (FileSystem fs = CloudStorageFileSystem.forBucket("bucket")) {
+      String pattern1 = "glob:*.java";
+      PathMatcher javaFileMatcher = fs.getPathMatcher(pattern1);
+      assertMatches(fs, javaFileMatcher, "a.java", true);
+      assertMatches(fs, javaFileMatcher, "a.text", false);
+      assertMatches(fs, javaFileMatcher, "folder/c.java", true);
+      assertMatches(fs, javaFileMatcher, "d", false);
+
+      String pattern2 = "glob:*.{java,text}";
+      PathMatcher javaAndTextFileMatcher = fs.getPathMatcher(pattern2);
+      assertMatches(fs, javaAndTextFileMatcher, "a.java", true);
+      assertMatches(fs, javaAndTextFileMatcher, "a.text", true);
+      assertMatches(fs, javaAndTextFileMatcher, "folder/c.java", true);
+      assertMatches(fs, javaAndTextFileMatcher, "d", false);
+    }
+  }
+
+  private void assertMatches(FileSystem fs, PathMatcher matcher, String toMatch, boolean expected) {
+    assertThat(matcher.matches(fs.getPath(toMatch).getFileName())).isEqualTo(expected);
+  }
 }