public int getSecondarySuccessor() {
    if (successors.size() != 2) {
      throw new UnsupportedOperationException("block doesn't have exactly two successors");
    }

    int succ = successors.get(0);
    if (succ == primarySuccessor) {
      succ = successors.get(1);
    }

    return succ;
  }
Gets the secondary successor of this block. It is only valid to call this method on blocks that
have exactly two successors.

@return {@code >= 0;} the secondary successor
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/code/BasicBlock.java