Java conventions for accessible data. (Public accessors & Getters/Naming)

Question

Through the Java API you see numerous occurrences of conflicting naming and practices which are really confusing to me.

For example:

The String class has a private variable (Integer) by the name of count which keeps track of the size of the string, however this is returned by a getter by the name of length().

If you move over to any type of arrays, instead of having a getter method for length, they just pass the variable through with a public accessor, and it can be obtained through arrayInstance.length.

Moving back to the String class we have the String#getBytes() method which is a getter, similar to the length() getter, however performs slightly more logic to get and return the value.

To me, personally, creating a getter with the prefix of get seems redundant, for example I rather type GamePacket#data() versus GamePacket#getData() however I feel like there may be a deeper meaning behind this naming instead of just inconsistency.

Also, why doesn't the Array[] use a getter for length?

Would anybody be kind enough to shed some light on this for me?

Answer 1

Getters (and setters) come from the Java Bean specification. The reasons to use them are multiple:

• most Java developers expect accessors to be named like that
• an API respecting these conventions is easier to discover. For example, in my IDE, I'll often press get CtrlSpace to discover all the information available in an object.
• many APIs and frameworks rely on these conventions to work: the JSP EL, MVC frameworks populating beans from request parameters, JPA, dependency injection frameworks like Spring, etc.

You usually name the getter the same way as the private variable that holds the information, but what matters is encapsulation and the public API, so nothing prevents you from computing a value in a getter, or to name the private field a different way.