content: /*
   *
   *  * Copyright 2020 Alibaba Group Holding Limited.
   *  *
   *  * 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 com.alibaba.graphscope.common.ir.meta;
  
  import com.google.common.base.Objects;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * This class is used to uniquely identify a graph instance in scenarios that support multiple graphs.
   * @param <T>
   */
  public class GraphId<T> {
      public static final GraphId DEFAULT = new GraphId(null);
  
      private final @Nullable T id;
  
      public GraphId(T id) {
          this.id = id;
      }
  
      public @Nullable T getId() {
          return id;
      }
  
      @Override
      public boolean equals(Object o) {
          if (this == o) return true;
          if (o == null || getClass() != o.getClass()) return false;
          GraphId<?> graphId = (GraphId<?>) o;
          return Objects.equal(id, graphId.id);
      }
  
      @Override
      public int hashCode() {
          return Objects.hashCode(id);
      }
  
      @Override
      public String toString() {
          return "GraphId{" + "id=" + id + '}';
      }
  }
  