Spring's transaction learning

Spring's default transaction isolation level Isolation_default is isolation_read_committed commit read, the default transactional propagation behavior is propagation_required, and if a transaction exists, the current transaction is supported. If there is no transaction, a new transaction is opened.

Here is a very interesting thing to share with you.

Class Sample{
　　private int id;
　　private String name;
　　//setters and getters
}
Class A {
　　public void functionA(Sample sample){
　　//事务处理，更新sample
　　}
}
class B {
　　public void functionB(List samples){
　　 //事务处理，遍历samples，调用A的functionA方法
　　}
}

I do not write the code in detail, the general meaning that everyone should be able to see that the isolation level of the transaction and propagation behavior are the default. What do you think will happen when you call the Functionb method of B?