content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you 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 io.ray.streaming.state.keystate.state.impl;
  
  import io.ray.streaming.state.backend.AbstractKeyStateBackend;
  import io.ray.streaming.state.keystate.desc.ListStateDescriptor;
  import io.ray.streaming.state.keystate.state.ListState;
  import java.util.ArrayList;
  import java.util.List;
  
  /** ListState implementation. */
  public class ListStateImpl<V> implements ListState<V> {
  
    private final StateHelper<List<V>> helper;
  
    public ListStateImpl(ListStateDescriptor<V> descriptor, AbstractKeyStateBackend backend) {
      this.helper = new StateHelper<>(backend, descriptor);
    }
  
    @Override
    public List<V> get() {
      List<V> list = helper.get();
      if (list == null) {
        list = new ArrayList<>();
      }
      return list;
    }
  
    @Override
    public void add(V value) {
      List<V> list = helper.get();
      if (list == null) {
        list = new ArrayList<>();
      }
      list.add(value);
      helper.put(list);
    }
  
    @Override
    public void update(List<V> list) {
      if (list == null) {
        list = new ArrayList<>();
      }
      helper.put(list);
    }
  
    @Override
    public void setCurrentKey(Object currentKey) {
      helper.setCurrentKey(currentKey);
    }
  }
  