Are getters and setters poor design? Contradictory

Question

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• Why use getters and setters/accessors? [closed] 38 answers

I'm currently working on a simple game in Java with several different modes. I've extended a main Game class to put the main logic within the other classes. Despite this, the main game class is still pretty hefty.

After taking a quick look at my code the majority of it was Getters and Setters (60%) compared to the rest that is truly needed for the logic of the game.

A couple of Google searches have claimed that Getters and Setters are evil, whilst others have claimed that they are necessary for good OO practice and great programs.

So what should I do? Which should it be? Should I be changing my Getters and Setters for my private variables, or should I stick with them?

Answer 1

Just FYI: In addition to all the excellent answers in this thread, remember that of all reasons you can come up with for or against getters/setters, performance isn't one (as some might believe). The JVM is smart enough to inline trivial getters/setters (even non-final ones, as long as they aren't actually overridden).

Answer 2

Getters and setters enforce the concept of encapsulation in object-oriented programming.

By having the states of the object hidden from the outside world, the object is truly in charge of itself, and cannot be altered in ways that aren't intended. The only ways the object can be manipulated are through exposed public methods, such as getters and setters.

There are a few advantages for having getters and setters:

1. Allowing future changes without modification to code that uses the modified class.

One of the big advantage of using a getter and setter is that once the public methods are defined and there comes a time when the underlying implementation needs to be changed (e.g. finding a bug that needs to be fixed, using a different algorithm for improving performance, etc.), by having the getters and setters be the only way to manipulate the object, it will allow existing code to not break, and work as expected even after the change.

For example, let's say there's a setValue method which sets the value private variable in an object:

public void setValue(int value)
{
    this.value = value;
}

But then, there was a new requirement which needed to keep track of the number of times value was changed. With the setter in place, the change is fairly trivial:

public void setValue(int value)
{
    this.value = value;
    count++;
}

If the value field were public, there is no easy way to come back later and add a counter that keeps track of the number of times the value was changed. Therefore, having getters and setters are one way to "future-proof" the class for changes which may come later.

2. Enforcing the means by which the object can be manipulated.

Another way getters and setters come in handy is to enforce the ways the object can be manipulated, therefore, the object is in control of its own state. With public variables of an object exposed, it can easily be corrupted.

For example, an ImmutableArray object contains an int array called myArray. If the array were a public field, it just won't be immutable:

ImmutableArray a = new ImmutableArray();
int[] b = a.myArray;
b[0] = 10;      // Oops, the ImmutableArray a's contents have been changed.

To implement a truly immutable array, a getter for the array (getArray method) should be written so it returns a copy of its array:

public int[] getArray()
{
    return myArray.clone();
}

And even if the following occurs:

ImmutableArray a = new ImmutableArray();
int[] b = a.getArray();
b[0] = 10;      // No problem, only the copy of the array is affected.

The ImmutableArray is indeed immutable. Exposing the variables of an object will allow it to be manipulated in ways which aren't intended, but only exposing certain ways (getters and setters), the object can be manipulated in intended ways.

I suppose having getters and setters would be more important for classes which are part of an API that is going to be used by others, as it allows keeping the API intact and unchanged while allowing changes in the underlying implementation.

With all the advantages of getters and setters said, if the getter is merely returning the value of the private variable and the setter is merely accepting a value and assigning it to a private variable, it seems the getters and setter are just extraneous and really a waste. If the class is going to be just for internal use by an application that is not going to be used by others, using getters and setters extensively may not be as important as when writing a public API.

Answer 3

I've been programming in java for few monts ago, and I've learned that we should use getters & setters only when it's necessary for the application

have fun :)

Answer 4

My opinion is that getters and setters are a requirement for good programs. Stick with them, but don't write unnecessary getters/setters - it's not always necessary to directly deal with all variables.

Answer 5

Your Game class is probably following the god object antipattern if it exposes that many variables. There's nothing wrong with getters and setters (though their verbosity in Java can be a bit annoying); in a well-designed app where each class has a clearly separated functionality, you will not need dozens of them in a single class.

Edit: If the main point for the getters and setters is to "configure" the game classe (I understand your comment that way), then your probably don't need the getters (it's perfectly fine for a class to access its own private variables without using get methods), and you can probably collapse many of the setters into "group setters" that set several variables which belong together conceptually.

Answer 6

There is also the point of view that most of the time, using setters still breaks encapsulation by allowing you to set values that are meaningless. As a very obvious example, if you have a score counter on the game that only ever goes up, instead of

// Game
private int score;
public void setScore(int score) { this.score = score; }
public int getScore() { return score; }
// Usage
game.setScore(game.getScore() + ENEMY_DESTROYED_SCORE);

it should be

// Game
private int score;
public int getScore() { return score; }
public void addScore(int delta) { score += delta; }
// Usage
game.addScore(ENEMY_DESTROYED_SCORE);

This is perhaps a bit of a facile example. What I'm trying to say is that discussing getter/setters vs public fields often obscures bigger problems with objects manipulating each others' internal state in an intimate manner and hence being too closely coupled.

The idea is to make methods that directly do things you want to do. An example would be how to set enemies' "alive" status. You might be tempted to have a setAlive(boolean alive) method. Instead you should have:

private boolean alive = true;
public boolean isAlive() { return alive; }
public void kill() { alive = false; }

The reason for this is that if you change the implementation that things no longer have an "alive" boolean but rather a "hit points" value, you can change that around without breaking the contract of the two methods you wrote earlier:

private int hp; // Set in constructor.
public boolean isAlive() { return hp > 0; } // Same method signature.
public void kill() { hp = 0; } // Same method signature.
public void damage(int damage) { hp -= damage; }