content: /*
   * Copyright (C) 2006 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package android.webkit;
  
  import android.annotation.Nullable;
  
  import java.io.Serializable;
  
  /**
   * This class contains the back/forward list for a WebView.
   * WebView.copyBackForwardList() will return a copy of this class used to
   * inspect the entries in the list.
   */
  public abstract class WebBackForwardList implements Cloneable, Serializable {
      /**
       * Return the current history item. This method returns {@code null} if the list is
       * empty.
       * @return The current history item.
       */
      @Nullable
      public abstract WebHistoryItem getCurrentItem();
  
      /**
       * Get the index of the current history item. This index can be used to
       * directly index into the array list.
       * @return The current index from 0...n or -1 if the list is empty.
       */
      public abstract int getCurrentIndex();
  
      /**
       * Get the history item at the given index. The index range is from 0...n
       * where 0 is the first item and n is the last item.
       * @param index The index to retrieve.
       */
      public abstract WebHistoryItem getItemAtIndex(int index);
  
      /**
       * Get the total size of the back/forward list.
       * @return The size of the list.
       */
      public abstract int getSize();
  
      /**
       * Clone the entire object to be used in the UI thread by clients of
       * WebView. This creates a copy that should never be modified by any of the
       * webkit package classes. On Android 4.4 and later there is no need to use
       * this, as the object is already a read-only copy of the internal state.
       */
      protected abstract WebBackForwardList clone();
  }
  