Basic Java Concepts

Question

I'm a Java novice, trying to learn it along with Jdeveloper side by side. My learning of the Java fundamental concepts led to the below understanding, please see if my understanding is not correct in any way.
The fundamental concept with Java is a CLASS, whose feature are its state and behaviour. The state of the class is stored in the definition of the class itself via ATTRIBUTES or in lay man's language VARIABLES. These attributes can be static, public, private or protectd.
The behaviour of a class is stored via METHODS within the definition of a class. METHOD is nothing but a block of code performaing a certain action.
A good example of a CLASS's state a behaviour can be a stock. A stocks state is available via its ticker symbol, price of the stock, and the date i.e. on a given date, a given stock has a particular price. So there are 3 attributes.
Now METHOD in the context of the above example is a means to capture the ever changing state of the above 3 attributes.
In short attributes or fields ( defined via declaration of variables inside the class) capture the state of an object, where as its interaction with the world external to the object captured by METHOD.
These 3 attributes are common to thousands of stock's in the outside market, so a common class called STOCK can be created to capture the state and behaviour of thousands of stocks. The same class can be called at the same time to capture the behaviour of N number of stocks. When a class is called as explained, each such call is called an INSTANCE of the CLASS. An OBJECT is an instance of SUCH a class.
Similar to CLASS is INTERFACE. A given class can only call the attributes and methods from one another class. If a class needs to inherit from more than one another class then it is accomplished via an INTERFACE. An Interface contains only the spec of the methods from other classes and not the entire piece of code for he method itself. The methods that are declared in the interface are implemented in the classes to which they belong to.
A PACKAGE in turn is a collected of CLASSES and INTERFACES. A PACKAGE helps in keeping the code oraganized and grouped by the functionaliy it delivers.
A Class can in turn be either a SUPERCLASS or a SUBCLASS. In our given example CLASS, there are some stocks which offer OPTIONS and some which do not. In order to cover that behaviours we will like to create sub class called STOCSKWITHOPTIONS, which will then refer to STOCK class to inherit the attributes and methods from that class. In this case STOCK is the SUPERCLASS, and STOCKOPTIONS is the SUBCLASS.
Thanks in advance

Answer 1

Nagarjuna,
there is an excellent tutorial series from Sun for basic and advanced Java features. It contains a lot of examples and explains every concept. You even download the tutorials.
See http://java.sun.com/javase/reference/tutorials.jsp
--olaf