@Test
  public void directedNetwork() {
    testNetworkMutation(NetworkBuilder.directed());
  }

  @Test
  public void undirectedNetwork() {
    testNetworkMutation(NetworkBuilder.undirected());
  }

  private static void testNetworkMutation(NetworkBuilder<? super Integer, Object> networkBuilder) {
    Random gen = new Random(42); // Fixed seed so test results are deterministic.

  }

  private static MutableNetwork<Integer, String> createNetwork(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return NetworkBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

  }

  private static MutableNetwork<Integer, String> createNetwork(EdgeType edgeType) {
    switch (edgeType) {
      case UNDIRECTED:
        return NetworkBuilder.undirected().allowsSelfLoops(true).build();
      case DIRECTED:
        return NetworkBuilder.directed().allowsSelfLoops(true).build();
    }
    throw new IllegalStateException("Unexpected edge type: " + edgeType);
  }

 * create an instance of one of the built-in implementations of {@code Network}, use the {@link
 * NetworkBuilder} class:
 *
 * <pre>{@code
 * MutableNetwork<Integer, MyEdge> network = NetworkBuilder.directed().build();
 * }</pre>
 *
 * <p>{@link NetworkBuilder#build()} returns an instance of {@link MutableNetwork}, which is a

import com.google.common.collect.ImmutableSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * Standard implementation of {@link Network} that supports the options supplied by {@link
 * NetworkBuilder}.
 *
 * <p>This class maintains a map of nodes to {@link NetworkConnections}. This class also maintains a
 * map of edges to reference nodes. The reference node is defined to be the edge's source node on

import com.google.common.collect.ImmutableSet;
import java.util.Map;
import java.util.Set;
import java.util.TreeMap;

/**
 * Standard implementation of {@link Network} that supports the options supplied by {@link
 * NetworkBuilder}.
 *
 * <p>This class maintains a map of nodes to {@link NetworkConnections}. This class also maintains a
 * map of edges to reference nodes. The reference node is defined to be the edge's source node on

    undirectedGraph = mutableUndirectedGraph;

    MutableNetwork<Integer, String> mutableDirectedNetwork =
        NetworkBuilder.directed().allowsParallelEdges(true).allowsSelfLoops(true).build();
    MutableNetwork<Integer, String> mutableUndirectedNetwork =
        NetworkBuilder.undirected().allowsParallelEdges(true).allowsSelfLoops(true).build();

import com.google.errorprone.annotations.CanIgnoreReturnValue;

/**
 * Standard implementation of {@link MutableNetwork} that supports both directed and undirected
 * graphs. Instances of this class should be constructed with {@link NetworkBuilder}.
 *
 * <p>Time complexities for mutation methods are all O(1) except for {@code removeNode(N node)},
 * which is in O(d_node) where d_node is the degree of {@code node}.
 *
 * @author James Sexton

    this.allowsParallelEdges = allowsParallelEdges;
    this.nodeOrder = nodeOrder;
    this.edgeOrder = edgeOrder;
  }

  @Override
  MutableNetwork<Integer, String> createGraph() {
    return NetworkBuilder.directed()
        .allowsSelfLoops(allowsSelfLoops)
        .allowsParallelEdges(allowsParallelEdges)
        .nodeOrder(nodeOrder)
        .edgeOrder(edgeOrder)
        .build();
  }

  @Override

    this.allowsParallelEdges = allowsParallelEdges;
    this.nodeOrder = nodeOrder;
    this.edgeOrder = edgeOrder;
  }

  @Override
  MutableNetwork<Integer, String> createGraph() {
    return NetworkBuilder.undirected()
        .allowsSelfLoops(allowsSelfLoops)
        .allowsParallelEdges(allowsParallelEdges)
        .nodeOrder(nodeOrder)
        .edgeOrder(edgeOrder)
        .build();
  }

  @Override