Java - how to stop data being edited upon an instance of it being created

Question

I am wondering how would I ensure that when an instance has been created that it is then impossible to change whatever is being passed through that instance. Therefore data can only can be created once.

I have a class with get and set methods of an accountNo and SortCode, how would I ensure that when this instance is called within a main method, then it can't be changed afterwords.

Thanks

You dont need set methods if you dont want them to be changed — Michael Grinnell, May 03 '17 at 16:49
See also Joshua Bloch's book "Effective Java", items 15: Minimize mutability and 39: Make defensive copies when needed. Summary: no mutators, prevent subclassing, all fields final and private, make defensive copies of any mutable objects passed into or out of the class. — Andy Thomas, May 03 '17 at 20:40

score 2 · Answer 1 · answered May 03 '17 at 16:47

2

Make the fields final.

final int accountNo;

answered May 03 '17 at 16:47

LLL

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This is helpful, but by no means sufficient. – Andy Thomas May 03 '17 at 20:37

score 0 · Answer 2 · answered May 03 '17 at 16:48

0

you need a strategy defining your objects Immutable

how:

declare members as final
don't provide setters
don't let subclass to override methods

check the Immutable RGB example here

answered May 03 '17 at 16:48

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Java - how to stop data being edited upon an instance of it being created

2 Answers2