Lets have a look at the road segment class. Part of it is shown here.
class RoadSegmentThis starts with a class definition- the word class followed by the class name just like in C++. This class has 3 fields all declared private. A field holds the data in the class- it''s just a variable.
{
private int length=1000; // length in feet
private int topSpeed = 30;
private bool lastSegment = false;
public int Length
{
get { return length; }
}
}
Generally you should always make fields private so that nothing outside the class can alter them. You wouldn't want to touch the insides of a television- you could damage the TV (and yourself!) and in OOP, it's the same principle. Two of these fields are ints they hold integer values in the range -2,147,483,648 to 2,147,483,647. The third one is a bool which only has two values: false or true.
It is all too easy to declare public fields but this is a bad habit so please don't do it. But how then do you access the values from outside of the object if they are declared to be private? By declaring a property and using it. I've shown just the one property for Length but in the full listing I've also defined them for the other fields. This property is read only- you can't change it.
On the next page : How to use Properties
