recently i read the book Hibernate in Action.in page 97,when I read another issue to consider is dirty checking,I don't undenstand the below example can avoid the property of a javabean SQL UPDATE:

public String getFirstname() {
return new String(firstname);
}
.

Maybe I don't understand the Hibernate completely,who can say it clearly.
Thanks.

What part don't you understand? Have you continued reading?

in page 97 in Hibernate ,the chaper:
3.2.5 Adding logic to accessor methods:

Another issue to consider is dirty checking. Hibernate automatically detects
object state changes in order to synchronize the updated state with the database.
It’s usually completely safe to return a different object from the getter method to
the object passed by Hibernate to the setter. Hibernate will compare the objects
by value—not by object identity—to determine if the property’s persistent state
needs to be updated. For example, the following getter method won’t result in
unnecessary SQL UPDATEs:
public String getFirstname() {
return new String(firstname);
}

I don't understand why the accessor method can avoid the SQL UPDATES.

Do you understand the difference between "pass by value" and "pass by reference" in Java?

thank u alert me .I understand it.thanks.