public Builder setTarget(
          org.box2d.proto.Box2D.PbVec2.Builder builderForValue) {
        if (targetBuilder_ == null) {
          target_ = builderForValue.build();
          onChanged();
        } else {
          targetBuilder_.setMessage(builderForValue.build());
        }
        bitField0_ |= 0x04000000;
        return this;
      }