Why do most fields (class members) in Android tutorial start with `m`?

A lot of coding guide lines use m for 'members' of a class. So when you're programming you can see the difference between local and member variables.

If it's member variables in classes, the 'm' means 'member'. Many Java programmers do that, although with modern IDEs it's not needed since you have highlighting, mouse over tooltips, etc.

I think it is very individual which code conventions is used. I prefer to name my variables with the following prefixes:

• m - Method variables
• c - Class variables
• p - Parameter variables

But I guess that each programmer has their own style.

It can also be stated that it stand for "mine", as in the Class/Instance is saying "This variable is mine and no one else can get to it." Different to static which, while it might be available to only the Class it is shared by all instances of that class. Like if you were drawing circles you'd need to know how big the radius of each circle is

    private double mRadius;

but at the same time you want a counter to keep track of all circles, inside of the circle class you could have

    private static int sCircleCount;

and then just have static members to increase and decrease the count of the circles you currently have.

The following are the naming conventions,

• Non-public, non-static field names start with m.
• Static field names start with s.
• Other fields start with a lower case letter.
• Public static final fields (constants) are ALL_CAPS_WITH_UNDERSCORES.

Example:

public class MyClass {
    public static final int SOME_CONSTANT = 42;
    public int publicField;
    private static MyClass sSingleton;
    int mPackagePrivate;
    private int mPrivate;
    protected int mProtected;
}