Review: array of primitive variables

Previously, we learned how to create an array of primitive typed variables:

double[] numbers; Result: numbers = new double[100]; Result:

Note: numbers[i] is a double variable and can store a number

Array of of reference variables that point to objects

Similiarly, you can create an array of reference variables:

Circle[] circleArray; Result: circleArray = new Circle[10]; Result:

Note: circleArray[i] is a Circle reference variable and can store a reference to a Circle object

What is an array of reference variables ?

What is an array of primitive typed variables and an array of reference variables:

After creating an array of primitive variables, each array element can store a number:

double[] numbers = new double[100]; numbers[0] = 99; // We can store a number

After creating an array of reference variables, each array element can store a reference of an object:

Circle[] circleArray = new Circle[10]; circleArray[0] = new Circle(2.0); // Stores a reference to a circle object

Important similarity (understanding an array)

Important similarity between an array of primitive typed variables and an array of reference variables:

Each array element of an array of double[] is a double typed variable:

double[] numbers = new double[100]; numbers[0] = 99; sum = sum + numbers[0]; // number[0] is a double

Each array element of an array of Circle[] is a Circle reference variable:

Circle[] circleArray = new Circle[10]; circleArray[0] = new Circle(2.0); double area = circleArray[0].getArea(); // circleArray[0] is a Circle reference

Using an array of objects

Array of objects is frequently used in computer programs
In the next set of slides, I will show you how to use an array of Card to represent a deck of playing cards