android/guava/src/com/google/common/graph/AbstractBaseGraph.java
protected long edgeCount() {
    long degreeSum = 0L;
    for (N node : nodes()) {
      degreeSum += degree(node);
    }
    // According to the degree sum formula, this is equal to twice the number of edges.
    checkState((degreeSum & 1) == 0);
    return degreeSum >>> 1;
  }
protected long edgeCount() {
    long degreeSum = 0L;
    for (N node : nodes()) {
      degreeSum += degree(node);
    }
    // According to the degree sum formula, this is equal to twice the number of edges.
    checkState((degreeSum & 1) == 0);
    return degreeSum >>> 1;
  }
protected long edgeCount ( ) { long degreeSum = 0L ; for ( N node : nodes ( ) ) { degreeSum += degree ( node ) ; } // According to the degree sum formula, this is equal to twice the number of edges. checkState ( ( degreeSum & 1 ) == 0 ) ; return degreeSum >>> 1 ; }
Returns the number of edges in this graph; used to calculate the size of {@link #edges()}. This
implementation requires O(|N|) time. Classes extending this one may manually keep track of the
number of edges as the graph is updated, and override this method for better performance.
Returns the number of edges in this graph ; used to calculate the size of {