* CompactHashMap.
   */

  private Object requireTable() {
    return requireNonNull(table);
  }

  private int[] requireEntries() {
    return requireNonNull(entries);
  }

  private @Nullable Object[] requireElements() {
    return requireNonNull(elements);
  }

  @SuppressWarnings("unchecked")
  private E element(int i) {
    return (E) requireElements()[i];

    IdentityHashMap<Entry<K, V>, Boolean> duplicates = null;
    int dupCount = 0;
    for (int entryIndex = n - 1; entryIndex >= 0; entryIndex--) {
      // requireNonNull is safe because the first `n` elements have been filled in.
      Entry<K, V> entry = requireNonNull(entryArray[entryIndex]);
      K key = entry.getKey();
      V value = entry.getValue();
      checkEntryNotNull(key, value);

    /**
     * Creates a new source backed by the specified URL.
     *
     * @param url The file, must not be {@code null}.
     */
    public UrlSource(URL url) {
        this.url = Objects.requireNonNull(url, "url cannot be null");
        this.hashCode = Objects.hashCode(url);
    }

    @Override
    public InputStream getInputStream() throws IOException {
        return url.openStream();
    }

import static com.google.common.collect.CollectPreconditions.checkNonnegative;
import static com.google.common.collect.CollectPreconditions.checkRemove;
import static java.util.Objects.requireNonNull;

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.primitives.Ints;

      }
      // re-read valueField, if we get here then we must have observed a TOMBSTONE while trying to
      // add a waiter.
      // requireNonNull is safe because valueField is always set before TOMBSTONE.
      return getDoneValue(requireNonNull(valueField));
    }
    // If we get here then we have remainingNanos < SPIN_THRESHOLD_NANOS and there is no node on the
    // waiters list

      Entry<Object, V>[] entries = new Entry[size];
      for (int i = 0; i < size; i++) {
        // requireNonNull is safe because the first `2*size` elements have been filled in.
        Object key = requireNonNull(alternatingKeysAndValues[2 * i]);
        @SuppressWarnings("unchecked")
        V value = (V) requireNonNull(alternatingKeysAndValues[2 * i + 1]);
        entries[i] = new AbstractMap.SimpleImmutableEntry<Object, V>(key, value);

      public @Nullable V remove(@Nullable Object key) {
        V value = get(key);
        if (value != null) {
          // it's definitely in the map, so the cast and requireNonNull are safe
          @SuppressWarnings("unchecked")
          Range<K> range = (Range<K>) requireNonNull(key);
          TreeRangeMap.this.remove(range);
          return value;
        }
        return null;
      }

      @Override

      checkState(
          state == FAILED,
          "failureCause() is only valid if the service has failed, service is %s",
          state);
      // requireNonNull is safe because the constructor requires a non-null cause with state=FAILED.
      return requireNonNull(failure);
    }
  }

      for (N successorNode : graph.successors(node)) {
        if (subgraph.nodes().contains(successorNode)) {
          // requireNonNull is safe because the endpoint pair comes from the graph.
          subgraph.putEdgeValue(
              node,
              successorNode,
              requireNonNull(graph.edgeValueOrDefault(node, successorNode, null)));
        }
      }
    }
    return subgraph;
  }

  /**

      for (N successorNode : graph.successors(node)) {
        if (subgraph.nodes().contains(successorNode)) {
          // requireNonNull is safe because the endpoint pair comes from the graph.
          subgraph.putEdgeValue(
              node,
              successorNode,
              requireNonNull(graph.edgeValueOrDefault(node, successorNode, null)));
        }
      }
    }
    return subgraph;
  }

  /**