- If a value of some value type is supplied in a context that requires an object (an instance of some class type), an object will automatically be created.
- This is called boxing.
-
Like Java, the
.NET Framework has a collection class called
ArrayList.
This is a class that can be used for a dynamic array:
ArrayList tArrayList = new ArrayList();
-
i = 27; tArrayList.Add(i);
an object is automatically created.
-
Point tPoint = new Point(100, 200); tArrayList.Add(tPoint);
- This is as in Java.
-
If instead we use a struct type, boxing takes place:
SPoint tSPoint = new SPoint(300, 400); tArrayList.Add(tSPoint);
- In Java, the only value types are the primitive types; and each primitive type has an associated wrapper type.
-
In Java, you have to do the boxing explicitly:
int i = 27; Integer tInteger = new Integer(i); tArrayList.Add(tInteger);
- In Java, a cast has to be used to get an object from an ArrayList.
- This is also the case in C#.
- If the cast is to a value type, unboxing automatically occurs.
-
This means the value of the object is copied into the variable:
int j = (int) tArrayList[0]; Point tGotPoint = (Point) tArrayList[1]; SPoint tGotSPoint = (SPoint) tArrayList[2];