SE450: Java: Object Creation [20/22]

How are objects specified and created?

Prototype-based languages allow the static description of objects (as literal values). To create new objects at runtime, they use cloning. JavaScript is an example of a prototype-based language. It doesn't distinguish between classes and instances. Any object can be used to create a new object by cloning it.

In JavaScript, an object can go from String to Integer to String without being re-instantiated.

Class-based language allow the static description of classes. To create objects at runtime, use a constructor.

When a reference type is created, only a storage location for the reference is made, not the objects themselves.

        Point p;            // reference variable of type Point
        p = new Point();    // new Instance of point
        int[] ia;           // reference variable of array of integers
        ia = new int[3];    // an array of size 3
        Point[] pArray;     // reference variable of array of Points
        pArray = new Point[3];  // an array of Points.  They are all null!
        // can use an array initializer
        ia = {1,2,3};
        pArray = { new Point(), new Point() } ;