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Posts Tagged ‘api’

Creating and using objects in Java

November 11, 2009 Leave a comment

 

Module 2: Creating and using objects.

 

Objectives:

  • Declaring object references, instantiating objects, and intializing object reference variables.
  • Compare how object reference variables are stored in relation to primitive variables.
  • Use a class (the String class) included in the Java SDK.
  • Use the J2SE class library specification to learn about other classes in this API.

 

In the previous module we discussed about primitive data types and how to use them with variables. In this module we will be focussing about objects and object reference variables. We will learn how object reference variables are stored in memory with reference to local variables. We will also take a look into the String class, as well as the class library specification to know about the other classes that we have access to.

 

1. Declaring object references, instantiating objects, and intializing object reference variables:

In the previous module we were dealing with primitive data types. And when we declared a variable of  a primitive datatype, we stored the primitive in the variable itself. But Java is object oriented language, so we really want to be dealing with objects. While dealing with objects you will also need a variable associated with it. But it works different with the objects. You dont store an object inside of a variable like you do with the primitives. What you do is, you store a reference to the object inside the variable.

Now a reference is like an address to a house. It allows you to find that object. So using that reference we can call up that object and ask it to do something. We can either access its attributes, or we can access its methods. Just like we can send a letter to a house as we have its address, we can access an object using its reference.

 

object reference

 

 

 

Example: Declaring object references:

Here we have the ShirtTest class that we used in the previous module to create a Shirt object and then access it. In the following sections we will take a detailed look at the creation of myShirt object refernce variable and the creation of the Shirt object and how these two are tied together and how the myShirt object reference variable is used to access the Shirt object.  

 

 ShirtTest class

 

 

Declaring object reference variables: Read more…

Explaining Java Technology

November 6, 2009 Leave a comment

  

Module 1 – Explaining Java Technology.

 

Objective:

Upon completion of reading this post, you should be able to know:

  • Key concepts of Java programming language.
  • Three Java technology product groups.
  • Seven stages of product life cycle.

 

 

Key concepts of Java programming language:

Java programming language originated in Sun Microsystems in 1999 as part of a research project to develop a programming language calld oak that would bridge the communication gap between many consumer devices such as video casette recorders & TV. Specifically, a team called green team wanted to create a software programming language enabling consumer devices with different CPU to share same software enhnacements.

 

 

1. green team

 

Initial concept failed as several deals with consumer companies were unsuccessful. So green team had to find another market. At that time www was becoming popular, and green team recognized tht the Oak language was perfect for developing web multimedia components to enhance web pages. Initially, small programs called applets became extensively used and gradually internet developers adopted what now is known as Java.

2. green team with internet

 

 

Java was designed to be: Read more…