Zhang Jie opened SPR-16809 and commented
Using "internalSet" instead of normal setter can avoid checking int param, because if constants.asNumber() works as expected and does't throw exception, the param checking in normal setter will never fail.
Affects: 5.0.6
Referenced from: pull request https://github.com/spring-projects/spring-framework/pull/1825
Comment From: snicoll
You are correct but the delegation is to make sure that there is a single place that mutates the parameter. In practice, the optimization is not worth the additional code.