public Builder setGroundAnchorA(
          org.box2d.proto.Box2D.PbVec2.Builder builderForValue) {
        if (groundAnchorABuilder_ == null) {
          groundAnchorA_ = builderForValue.build();
          onChanged();
        } else {
          groundAnchorABuilder_.setMessage(builderForValue.build());
        }
        bitField0_ |= 0x00080000;
        return this;
      }