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 org.apache.calcite.util.graph;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  import static java.util.Objects.requireNonNull;
  
  /**
   * Default implementation of Edge.
   */
  public class DefaultEdge {
    public final Object source;
    public final Object target;
  
    public DefaultEdge(Object source, Object target) {
      this.source = requireNonNull(source, "source");
      this.target = requireNonNull(target, "target");
    }
  
    @Override public int hashCode() {
      return source.hashCode() * 31 + target.hashCode();
    }
  
    @Override public boolean equals(@Nullable Object obj) {
      return this == obj
          || obj instanceof DefaultEdge
          && ((DefaultEdge) obj).source.equals(source)
          && ((DefaultEdge) obj).target.equals(target);
    }
  
    @Override public String toString() {
      return source + " -> " + target;
    }
  
    public static <V extends Object> DirectedGraph.EdgeFactory<V, DefaultEdge> factory() {
      // see https://github.com/typetools/checker-framework/issues/3637
      //noinspection Convert2MethodRef
      return (source1, target1) -> new DefaultEdge(source1, target1);
    }
  }
  