Java Classes |
Classes and Objects are the heart and
sould of the OOP (Object Oriented Programming) and without them OOP cannot
exist. In this lesson we will start our discussion on Java
classes. As C++ programmers, you will glad to know that Java classesare
almost the same as C++ classes. Like C++ classes, Java classescontain
fields also called instance variables or properties of an object and methods. A
field is like a C++ data member, and a method is like a C++ member
function.
A Simple Example Class
In the following example, a List is defined to be an ordered collection of items of any type:
A Simple Example Class
In the following example, a List is defined to be an ordered collection of items of any type:
class List {
// fields
private Object [ ] items; // store the items in an array
private int numItems; // the current # of items in the list
//methods
// constructor function
public List() {
items = new Object[10];
numItems = 0;
}
// AddToEnd: add a given item to the end of the list
public void AddToEnd(Object ob){
}
}
In Java, all classes
(built-in or user-defined) are (implicitly) subclasses of the classObject.
Using an array of Object in the List class allows any kind of Object
(an instance of any class) to be stored in the list. However, primitive
types (int, char, etc) cannot be stored in the list as they are not
inherited from Object.
