content: /*
   * The Alluxio Open Foundation licenses this work under the Apache License, version 2.0
   * (the "License"). You may not use this work except in compliance with the License, which is
   * available at www.apache.org/licenses/LICENSE-2.0
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
   * either express or implied, as more fully set forth in the License.
   *
   * See the NOTICE file distributed with this work for information regarding copyright ownership.
   */
  
  package alluxio.util;
  
  import alluxio.Constants;
  
  import java.io.File;
  import javax.annotation.concurrent.ThreadSafe;
  
  /**
   * Utility functions for working with extensions.
   */
  @ThreadSafe
  public final class ExtensionUtils {
  
    private static final File[] EMPTY_EXTENSIONS_LIST = new File[0];
  
    /**
     * List extension jars from the configured extensions directory.
     *
     * @param extensionDir the directory containing extensions
     * @return an array of files (one file per jar)
     */
    public static File[] listExtensions(String extensionDir) {
      File[] extensions = new File(extensionDir)
          .listFiles(file -> file.getPath().toLowerCase().endsWith(Constants.EXTENSION_JAR));
      if (extensions == null) {
        // Directory does not exist
        return EMPTY_EXTENSIONS_LIST;
      }
      return extensions;
    }
  
    private ExtensionUtils() {} // prevent instantiation
  }
  