Java Conventions: use getters/setters WITHIN the class?

Question

My professor really emphasizes protecting against privacy leaks by always using accessors and mutators to access private instance variables; however, do I have to use the getters/setters of a class within the class?

So for instance, if I have the following class:

public class Person  {     private String name;     private int age; } 

and I want to write a toString() method for it. Can I just write:

public String toString() {     return name + " " + age; } 

OR do I need to do something like this:

public String toString() {     return this.getName() + " " + this.getAge(); } 

Answer 1

You CAN do either one. However, your professor might appreciate using the methods instead of the direct access. Here's why.

Let's say you have a class like this:

class SomeClass {     private int someValue;     private String someString;      public SomeClass(int someValue, String someString) {         this.someValue = someValue;         this.someString = someString;     }      public int someValue() {         return this.someValue;     }      public String someString() {         return this.someString;     }      public String toString() {         return someValue + ": " + someString;     }  } 

It's pretty straightforward, right? Well, what if all of a sudden we want to CHANGE the implementation of how we calculate someValue, and base it off of someString:

public int someValue() {     int value = 0;     for(int i = 0; i < someString.length; i++) {          if(someString.charAt(i) == ' ') value++;     }     return value; } 

Now you also have to change every place where variable someValue was used.

So if you want to make the code easier to maintain in the long run, use the methods calls. This way when you code changes on you (and trust me, it changes all the time) you only have to change it in one spot instead of two.

And yes, you would want to use a method call in getting someString instead of the direct access in the last method :-)

Answer 2

When I design a class I try to make a clear distinction between the inside (implementation details) and the outside (the interface exposed to the world). Getters and setters provide a convenient place to convert values between the form in which they are stored in the object’s instance members and the form in which the outside world sees them. Using getters and setters internally would muck that up, because they'd be getting used by both the inside and outside.

If you find yourself wanting to hide part of a class from another part of the same class, consider breaking off the part you want to hide into its own class.