Is it bad practice to have my getter method change the stored value?

Question

Is it bad practice to change my getter method like version 2 in my class.

Version 1:

 public String getMyValue(){
     return this.myValue
 }
         


        

Answer 1

Yes. It's a bad practice.

Why?

When the value is set (in a constructor or setter method), it should be validated, not when a getter method is called. Creating a private validate* method for this is also a good idea.

private boolean validateThisValue(String a) {
     return this.myValue != null && !this.myValue.isEmpty();
}

public void setThisValue(String a) {
    if (validateThisValue(a)) {
        this.myValue = a;
    } 
    else {
        // do something else
        // in this example will be
        this.myValue = "N/A";
    }
}

And, in the getter method, never ever change the state of the object. I have worked on some projects, and the getter often must be made const: "this method cannot change internal state".

At least, if you do not want to complicate things, in the getter method, you should return "N/A" rather than change internal state and set myValue to "N/A".