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6. Enums
In case you don't know C, Enums let you specify a group of objects, e.g.:
Declaration:
public enum Direction {North, East, West, South};
Usage:
Direction wall = Direction.North;
It's a nice construct, so perhaps the question is not why did C# decide to have them, but rather, why did Java choose to omit them? In Java, you would have to go:
Declaration:
public class Direction {
public final static int NORTH = 1;
public final static int EAST = 2;
public final static int WEST = 3;
public final static int SOUTH = 4;
}
Usage:
int wall = Direction.NORTH;
Despite the fact the Java version seems to express more, it doesn't, and is less type-safe, by allowing you to accidentally assign wall to any int value without the compiler complaining. To be fair, in my experience of Java programming I haven't wasted much time on writing a few extra tokens and tracking down an error because of lack of type-safety here, but nonetheless, this is nice to have. One benefit of C# is the nice surprise you get when debugging - if you put a break point on an enumeration which holds combined enumerations, it will automatically decode direction to give you a human readable output, rather than a number you have to decode:
Declaration:
public enum Direction {North=1, East=2, West=4, South=8};
Usage:
Direction direction = Direction.North | Direction.West;
if ((direction & Direction.North) != 0)
....
If you put a breakpoint on the if statement, you'll get the human readable version for direction rather than the number 5.
7. Collections and the Foreach Statement
C# provides a shorthand for for-loops, which also encourages increased consistency for collections classes:
In Java or C++:
1. while (! collection.isEmpty()) {
Object o = collection.get();
collection.next();
...
2. for (int i = 0; i < array.length; i++)...
In C#:
1. foreach (object o in collection)...
2. foreach (int i in array)...
The C# for-loop will work on collection objects (arrays implement a collection). Collection objects have a GetEnumerator() method which returns an Enumerator object. An Enumerator object has a MoveNext method and a Current property.
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The mostly likely reason why enums are absent in Java is that you can get by using classes instead. As I mentioned in previous sections, with classes alone we are not able to express a feature in the world as well as we could with another construct. What are the benefits of the Java philosophy of "if it can be done by a class, then don't introduce a new construct"? It would seem simplicity would be the biggest benefit - a shorter learning curve and the prevention of programmers having to think of multiple ways of doing things. Indeed the Java language has improved on C++ in many ways by aiming for simplicity, such as the elimination of pointers, the elimination of header files, and a single-rooted object hierarchy. However, a common aspect of all these simplifications is they actually make coding - uh - simpler. Leaving out constructs, we've looked at enums, properties and events so far, makes your coding more complicated.