private com.google.protobuf.SingleFieldBuilder<
          org.box2d.proto.Box2D.PbVec2, org.box2d.proto.Box2D.PbVec2.Builder, org.box2d.proto.Box2D.PbVec2OrBuilder> 
          getLocalAxisAFieldBuilder() {
        if (localAxisABuilder_ == null) {
          localAxisABuilder_ = new com.google.protobuf.SingleFieldBuilder<
              org.box2d.proto.Box2D.PbVec2, org.box2d.proto.Box2D.PbVec2.Builder, org.box2d.proto.Box2D.PbVec2OrBuilder>(
                  localAxisA_,
                  getParentForChildren(),
                  isClean());
          localAxisA_ = null;
        }
        return localAxisABuilder_;
      }