CSE Lecture 6/Feb/2008

Mutators and Accessors in Compositions

-avoid privacy leaks
-make defensive copies whenever mutable objects are passed into or out of the composition. No changes are needed for immutable objects.

Mutator
-create a copy of the external object and start that in our object's attribute.

Accessor
-create a copy of the objects attribute and return that copy.

Constructor
-just like the mutator.

Copy Constructors of Compositions and Aggregates
-"deep copy" --> respect the semantics of the internal objects.

-composition: copy constructor also creates new copies of all internal mutable objects.
-aggregate: only copy references, do not create new copies of internal objects.

Arrays

-Array is similar to ArrayList
- a list of objects stores by index
- all objects of the same type

Array Syntax (starting with primitives)
e.g. a list of 5 integers: int[] x = new int[5]; //creates an empty array of 5 integers.
x.length gives you the length of the array (5 in this case)

e.g. I want to store the int 1024 in the first element of the array.
x[0] = 1024; //note that array indices, like ArrayList, start at zero.

Say you want to get the third element in the array and store it in a separate int.
int y;
y = x[2];

Arrays can be initialized at declaration.
int[] x = {1024,345,-2,123,81};