<\/p>\n
Are you following these fundamental principles?<\/p>\n
Just so we’re on the same page, an immutable object is on whose state cannot be changed after construction.<\/p>\n
This view is supported by Joshua Bloch in Effective Java (2nd). Item 13 states: “Minimize the accessibility of classes and members.”<\/p>\n
<\/p>\n
He goes on to say some fundamental principles.<\/p>\n
all <\/strong>of its implementation details, cleanly separating its API from its implementation. Modules then communicate only through their APIs and are oblivious to each others’ inner workings.”, “Joshua Bloch”, “Effective Java (2nd), page 67”) ?><\/p>\n
These are really the basics of information hiding or encapsulation. Basics of OOP programming! It’s a good idea to learn these well.<\/p>\n
Think twice before making any fields public. Hold it. No, don’t make it public! Think twice before making it any other than private!<\/p>\n
But to make sure you only expose what is absolutely needed requires some thought. You need your own judgment and experience.<\/p>\n
As for the second part, item 15 states: “Minimize mutability.”<\/p>\n
I think this one is a little harder to justify and not so obvious. But Bloch has some very good arguments. Together with Goetz, they convinced me that I should utilize immutability more often when I’m designing classes.<\/p>\n
<\/p>\n
Convinced!<\/p>\n
But how? Follow these 5 steps (as per Bloch).<\/p>\n
1. Don’t provide any methods that modify the object’s state.
\n2. Ensure the class can’t be extended.
\n3. Make all fields final.
\n4. Make all fields private.
\n5. Ensure exclusive access to any mutable components.<\/p>\n
Goets says it a little bit differently.<\/p>\n
An object is immutable<\/strong> if: One more time. Tell me what are the benefits of immutable objects<\/strong>!<\/p>\n They are simple to understand. Let’s end with a great summary note from Bloch, “Classes should be immutable unless there’s a very good reason to make t hem mutable.” <\/strong><\/p>\n But.<\/p>\n If…<\/p>\n “If a class cannot be made immutable, limit its mutablity as much as possible.”<\/strong><\/p>\n Strong statements.<\/p>\n Learn these design principles!<\/p>\n All in all, I recommend reading Item 15 from the Effective Java book. And re-read a few times until it becomes part of your design logic.<\/p>\n It’s all about getting better.<\/p>\n It’s all about improving.<\/p>\n
\n – Its state cannot be modified after construction;
\n – All its fields are final;
\n – It is properly constructed (the this reference does not escape during construction)
\nImmutable objects pack a lot of goodies in them.<\/p>\n
\nThey are thread safe.
\nThey require no synchronization.<\/p>\n