Java Programming Language - Getting Started

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In this chapter,  we will learn everything that we will need to know about getting started with the Java programming language.

Let's first look at an overview of Java technology as a whole. We will discuss both the Java programming language and platform, providing a broad overview of what this technology can do and how it will make your life easier.

1. About the Java Technology

Java technology is both a programming language and a platform.

The Java Programming Language

The Java programming language is a high-level language that can be characterized by all of the following buzzwords:
  1. Simple
  2. Object-oriented
  3. Distributed
  4. Multi-threaded
  5. Dynamic
  6. Architecture neutral
  7. Portable
  8. High performance
  9. Robust
  10. Secure
These buzzwords are explained nicely in my separate chapter at Java Buzzwords or Features of Java.
Now, let's briefly look at the Java software development process:


Step 1:  Create a Java Source File

Create a file named HelloWorldApp.java and add the following code to it: 
In the Java programming language, all source code is first written in plain text files ending with the .java extension. 
Don't worry about the source code that we will learn in the next chapters.

Step 2: Compile Java Source File

Use the javac compiler to compile the HelloWorldApp.java file to the HelloWorldApp.class file. A HelloWorldApp.class file does not contain code that is native to your processor; it instead contains bytecodes the machine language of the Java Virtual Machine (Java VM). 

For example -
javac HelloWorldApp.java

Step 3: Execute ByteCodes ( .class File)

Use the java launcher tool to execute HelloWorldApp.class (bytecodes) with an instance of the Java Virtual Machine. 

For example - 
java HelloWorldApp

2. Java Platform Independent

Java is platform-independent so Java can run on any operating system and hardware. Now the question is how is it platform independent?

This is because of the magic of byte-code which is OS independent. When Java compiler compiles any code then it generates the byte-code which is not the machine native code(unlike C compiler). 

This byte-code needs an interpreter to execute on a machine. This interpreter is JVM. So JVM reads that byte-code (that is machine-independent) and execute it. Different JVM is designed for different OS and byte-code is able to run on different OS.
From the above diagram, Java VM is available on many different operating systems, the same .class files are capable of running on Microsoft Windows, the Solaris Operating System (Solaris OS), Linux, or Mac OS. The bytecode is a platform-independent code because it can be run on multiple platforms, i.e., Write Once and Run Anywhere(WORA).

3. JVM Platform Dependent?

As we know that JVM translates the byte-code into machine language, and since the machine language depends on the operating system being used, it is clear that the JVM is platform (operating system) dependent. This fact can be verified by trying to download the JVM – you will be given a list of JVM’s corresponding to different operating systems, and you will obviously pick whichever JVM is targeted for the operating system that you are running.

4. The Java Platform

A platform is the hardware or software environment in which a program runs. We've already mentioned some of the most popular platforms like Microsoft Windows, Linux, Solaris OS, and Mac OS. Most platforms can be described as a combination of the operating system and underlying hardware. The Java platform differs from most other platforms in that it's a software-only platform that runs on top of other hardware-based platforms.

The Java platform has two components:
  1. The Java Virtual Machine
  2. The Java Application Programming Interface (API)
JVM (Java Virtual Machine) is an abstract machine. It is called a virtual machine because it doesn't physically exist. It is a specification that provides a runtime environment in which Java bytecode can be executed. It can also run those programs which are written in other languages and compiled to Java bytecode.

The API is a large collection of ready-made software components that provide many useful capabilities. It is grouped into libraries of related classes and interfaces; these libraries are known as packages. The next section, What Can Java Technology Do? highlights some of the functionality provided by the API.
As a platform-independent environment, the Java platform can be a bit slower than native code. However, advances in compiler and virtual machine technologies are bringing performance close to that of native code without threatening portability.

5. What Can Java Technology Do?

The general-purpose, high-level Java programming language is a powerful software platform. Every full implementation of the Java platform gives you the following features:

Development Tools: The development tools provide everything you'll need for compiling, running, monitoring, debugging, and documenting your applications. As a new developer, the main tools you'll be using are the javac compiler, the java launcher, and the Javadoc documentation tool.

Application Programming Interface (API): The API provides the core functionality of the Java programming language. It offers a wide array of useful classes ready for use in your own applications. It spans everything from basic objects, to networking and security, to XML generation and database access, and more. The core API is very large; to get an overview of what it contains, consult the Java Platform Standard Edition 8 Documentation.

Deployment Technologies: The JDK software provides standard mechanisms such as the Java Web Start software and Java Plug-In software for deploying your applications to end-users.

User Interface Toolkits: The JavaFX, Swing, and Java 2D toolkits make it possible to create sophisticated Graphical User Interfaces (GUIs).

Integration Libraries: Integration libraries such as the Java IDL API, JDBC API, Java Naming and Directory Interface (JNDI) API, Java RMI, and Java Remote Method Invocation over Internet Inter-ORB Protocol Technology (Java RMI-IIOP Technology) enable database access and manipulation of remote objects.

6. How Will Java Technology Change My Life?

As per Oracle official tutorial, the answer for this question - Java technology will help you do the following:

Get started quickly: Although the Java programming language is a powerful object-oriented language, it's easy to learn, especially for programmers already familiar with C or C++.

Write less code: Comparisons of program metrics (class counts, method counts, and so on) suggest that a program written in the Java programming language can be four times smaller than the same program written in C++.

Write better code: The Java programming language encourages good coding practices, and automatic garbage collection helps you avoid memory leaks. Its object orientation, its JavaBeans™ component architecture, and it's wide-ranging, easily extendible API let you reuse existing, tested code and introduce fewer bugs.

Develop programs more quickly: The Java programming language is simpler than C++, and as such, your development time could be up to twice as fast when writing in it. Your programs will also require fewer lines of code.

Avoid platform dependencies: You can keep your program portable by avoiding the use of libraries written in other languages.

Write once, run anywhere: Because applications written in the Java programming language are compiled into machine-independent bytecodes, they run consistently on any Java platform.

Distribute software more easily: With Java Web Start software, users will be able to launch your applications with a single click of the mouse. An automatic version check at startup ensures that users are always up to date with the latest version of your software. If an update is available, the Java Web Start software will automatically update their installation.

What's Next

In this chapter, we understood the basic terms of the Java Programming language. In the next chapter, we will create our first Java first hello-world program - how to create, compile and run a Java hello world program.

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