Java – Struct like objects in Java

javaoopstruct

Is it completely against the Java way to create struct like objects?

class SomeData1 {
    public int x;
    public int y;
}

I can see a class with accessors and mutators being more Java like.

class SomeData2 {
    int getX();
    void setX(int x);

    int getY();
    void setY(int y);

    private int x;
    private int y;
}

The class from the first example is notationally convenient.

// a function in a class
public int f(SomeData1 d) {
    return (3 * d.x) / d.y;
}

This is not as convenient.

// a function in a class
public int f(SomeData2 d) {
    return (3 * d.getX()) / d.getY();
}

Best Solution

It appears that many Java people are not familiar with the Sun Java Coding Guidelines which say it is quite appropriate to use public instance variable when the class is essentially a "Struct", if Java supported "struct" (when there is no behavior).

People tend to think getters and setters are the Java way, as if they are at the heart of Java. This is not so. If you follow the Sun Java Coding Guidelines, using public instance variables in appropriate situations, you are actually writing better code than cluttering it with needless getters and setters.

Java Code Conventions from 1999 and still unchanged.

10.1 Providing Access to Instance and Class Variables

Don't make any instance or class variable public without good reason. Often, instance variables don't need to be explicitly set or gotten-often that happens as a side effect of method calls.

One example of appropriate public instance variables is the case where the class is essentially a data structure, with no behavior. In other words, if you would have used a struct instead of a class (if Java supported struct), then it's appropriate to make the class's instance variables public.

http://www.oracle.com/technetwork/java/javase/documentation/codeconventions-137265.html#177

http://en.wikipedia.org/wiki/Plain_old_data_structure

http://docs.oracle.com/javase/1.3/docs/guide/collections/designfaq.html#28