Chapter 2 Software Programming Of Java 2 Lesson 1″ Like all other computer languages, the elements of Java do not exist in isolation. Rather, they work together to form the language as a whole. However, this Interrelates can make it difficult to describe one aspect of Java without involving several others.
Often a discussion of one feature implies prior knowledge of another. For this reason, this chapter presents a quick overview of several key features of Java.
Software Programming Of Java 2
The material described here will give you a foothold that will allow you to write and understand simple programs. Most of the topics discussed will be examined in greater detail in the remaining chapters of Part 1.
Object-oriented programming is at the core of Java. In fact, all Java programs are object- oriented-this isn’t an option the way that it is in C++,
OOP is so integral to Java that you must understand its basic principles before you can write even simple Java programs. Therefore, this chapter begins with a discussion of the theoretical aspects of OOP.
As you know, all computer programs consist of two elements: code and data. Furthermore, a program can be conceptually organized around its code or around its data.
That is, some programs are written around “what is happening” and others are written around. “who is being affected.” These are the two paradigms that govern how a program is constructed.
The first way is called the process-oriented model. This approach characterizes a program as a series of linear steps (that is, code). The process-oriented model can be thought of as code acting on data.
Procedural languages such as C employ this model to considerable success. However, as mentioned in Chapter 1, problems with this approach appear as programs grow larger and more complex.
To manage increasing complexity, the second approach, called object-oriented programming, was conceived. Object-oriented programming organizes a program around its data (that is, objects) and a set of well-defined interfaces to that data.
An object-oriented program can be characterized as data controlling access to code. As you will see, by switching the controlling entity to data, you can achieve several organizational benefits.
An essential element of object-oriented programming is abstraction. Humans manage complexity through abstraction.
people do not think of a car as a set of tens of thousands of individual parts. They think of it as a well-defined object with its own unique behavior.
This abstraction allows people to use a car to drive to the grocery store without being overwhelmed by the complexity of the parts that form the car. They can ignore the details of how the engine, transmission, and braking systems work. Instead they are free to utilize the object as a whole.
A powerful way to manage abstraction is through the use of hierarchical classifications. This allows you to layer the semantics of complex systems, breaking them into more manageable pieces. From the outside, the car is a single object. Once inside,
You see that the car consists of several subsystems: steering, brakes, sound system, seat belts, heating, cellular phone, and so on. In turn, each of these subsystems is made up of more specialized units. For instance, the sound system consists of a radio, a CD player, and/or a tape player.
The point is that you manage the complexity of the car (or any other complex system) through the use of hierarchical abstractions. Hierarchical abstractions of complex systems can also be applied to computer programs. The data from a traditional process-oriented program can be transformed by abstraction into its component objects.
A sequence of process steps can become a collection of messages between these objects. Thus, each of these objects describes its own unique behavior. You can treat these objects as concrete entities that respond to messages telling them to do something.
This is the essence of object-oriented programming. Object-oriented concepts form the heart of Java just as they form the basis for human understanding. It is important that you understand how these concepts translate into As you will see, object-oriented programming is a powerful and natural programs.
paradigm for creating programs that survive the inevitable changes accompanying the life cycle of any major software project, including conception, growth, and aging.
once you have well-defined objects and clean, reliable interfaces to those objects, you can gracefully decommission or replace parts of an older system without fear.
The Three OOP Principles:-
All object-oriented programming languages provide mechanisms that help you implement the object-oriented model, They are encapsulation, inheritance, and polymorphic. Let’s take a look at these concepts now.