6. Keeping Scopes Small

Data abstraction and hiding closely relates to the scopes of variables and operations.

In view of good design we must pursue the goal of localizing attributes and behaviors as much as possible.

This greatly improves debugging, testing, documentation, and extensibility of the entire system.

Keeping minimal scopes emphasizes good programming style.

Consider:

public class Math {
    int temp = 0;
    public int swap( int a, int b ) {
        temp = a;
        a = b;
        b = temp;
        return temp;
    }
}

Better:

public class Math {
    public int swap( int a, int b ) {
        int temp = 0;
        temp = a;
        a = b;
        b = temp;
        return temp;
    }
}