Java Introduction

This article explores the history, principles, and inner workings of Java, offering a complete overview of why it remains a powerful tool for building scalable and reliable applications. Java is one of the most used programming languages, known for its versatility, robustness, and platform independence. Since its inception in the early 1990s, Java has grown to become one of the most widely used high-level programming languages worldwide. It is a full-featured general-purpose language that allows the development of platform-independent software, running smoothly on desktop computers, mobile devices, and servers. Java's simplicity, object-oriented nature, and extensive features make it a preferred choice for developers across various fields, from enterprise solutions to mobile applications and web development.

What is Java?

Java is a powerful, versatile, and simple general-purpose programming language. It is one of the most widely used high-level programming languages in the world. Java is a full-featured general-purpose programming language that is used for developing platform-independent software (applications) running on desktop computers, mobile devices, and servers. It is a simple, object-oriented, distributed, interpreted, secure, robust, architecture neutral, portable, high performance, multithreaded, and dynamic programming language.

History of Java

In 1990, Sun Microsystems Inc. (US) imagined a project to develop software for consumer electronic devices that could be controlled by a remote. Initially, this project was named Stealth Project but later its name was changed to Green Project. In January of 1991, Bill Joy, James Gosling, Patrick Naughton, Mike Sheridan, and several others met in Aspen, Colorado to discuss this project. The job of Mike Sheridan was to focus on business development. Patrick Naughton was to work on the graphics system. James Gosling was to recognize the proper programming language for the project. He thought that C and C++ programming languages could be used to develop this project.

Naming of Java

This programming language was initially named Oak but later it was changed to Java in 1995. Thus, Java was developed by James Gosling, Patrick Naughton, Chris Warth, Ed Frank, and Mike Sheridan at Sun Microsystems in 1991. It took 18 months to develop the first working version of Java. James Gosling and his team members were consuming a lot of tea while developing the Java programming language. They felt that they had developed a better programming language because of the good quality tea they had consumed. Thus, the tea also had its own role in developing Java language. Hence, they kept the name for the language as Java. Since Java was so unique name, most of the team members preferred to name Java. Java is an island of Indonesia where the first time coffee was produced, was named java coffee. Java name was chosen by James Gosling while consuming coffee near his office during the development of java language. Thus, the symbol for Java is tea cup.

Oracle Corporation Acquired Sun Microsystems

Oracle Corporation acquired Sun Microsystems on January 27, 2010, and is the owner of Java SE implementations. The Oracle implementation of Java SE is available for Microsoft Windows, Mac OS X, Solaris, and Linux.

Java Programming Language Platforms

• Java SE/J2SE (Java Standard Edition)

• Java EE/J2EE (Java Enterprise Edition)

• Java ME/J2ME (Java Micro Edition)

• JavaFX

History of Java Versions

Several Java versions have been released till now. They are as follows:

• JDK Alpha and Beta (1995): The JDK Alpha and Beta was the first release in 1995 but they have highly unstable APIs and ABIs.

• JDK 1.0 (23rd Jan 1996): JDK 1.0 was the first stable released version of Java. Its code name was Oak. The first stable version of JDK was JDK 1.0.2 and it was named Java 1.

• JDK 1.1 (19th Feb 1997)

• J2SE 1.2 (8th Dec 1998)

• J2SE 1.3 (8th May 2000)

• J2SE 1.4 (6th Feb 2002)

• J2SE 5.0 (30th Sep 2004)

• Java SE 6 (11th Dec 2006)

• Java SE 7 (28th July 2011)

• Java SE 8 (18th Mar 2014)

• Java SE 9 (21st Sep 2017)

• Java SE 10 (20th Mar 2018)

For more detailed version of Java, go to this link: Java version history

Principles of Java

• High-level programming language: Java is designed to be easy to read and write, making it accessible to a wide range of developers.

• Object-oriented programming language: Java uses objects to represent data and methods, promoting code reuse and modularity.

• Robust: Java emphasizes early checking for possible errors, as well as runtime checking, to ensure reliable code.

• Scalable: Java can be used to build applications that scale from small to large, handling increasing loads efficiently.

• Secured: Java provides a secure environment for developing and running applications, with built-in security features.

• Powerful: Java offers a rich set of APIs and tools for building a wide variety of applications.

• High performance: Java's Just-In-Time (JIT) compiler and efficient memory management contribute to its high performance.

• Stable: Java's backward compatibility ensures that older applications continue to work with newer versions of the language.

• Threaded: Java supports multithreading, allowing multiple threads to run concurrently within a program.

• Dynamic: Java can adapt to an evolving environment, with features like dynamic class loading.

• Easy to develop: Java's syntax and extensive libraries make it easy to develop applications quickly.

• Platform-independent: Java applications can run on any device with a Java Virtual Machine (JVM), making them highly portable.

Key Features of Java

Java Development Kit (JDK), Java Runtime Environment (JRE), and Java Virtual Machine (JVM)

• JDK (Java Development Kit): The JDK is a software development kit used to develop Java applications. It includes the JRE, an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (Javadoc), and other tools needed for Java development.

• JRE (Java Runtime Environment): The JRE provides the libraries, Java Virtual Machine (JVM), and other components to run applications written in Java. It does not include development tools such as compilers or debuggers.

• JVM (Java Virtual Machine): The JVM is a part of the JRE that executes Java bytecode. It provides a platform-independent way of executing code, meaning that Java applications can run on any device that has a compatible JVM.

  JDK (Java Development Kit)	Development Tools + JRE
  JRE (Java Runtime Environment)	Runtime Libraries + JVM
  JVM (Java Virtual Machine)	Bytecode Verifier, Interpreter, JIT Compiler

• Development Tools: javac (compiler), java (runtime), jar (archiver), javadoc (documentation generator), debugger, etc.

• Runtime Libraries: Class libraries for Java API (e.g., java.lang, java.util, javax.swing).

• Each component builds upon the others, with the JVM at the core of Java's "Write Once, Run Anywhere" philosophy.

How Java Works Internally

We will explore this in detail later to gain a deeper understanding of the language, but here is a brief about how java works.

1. Compilation: Java source code (.java files) is compiled by the Java compiler (javac) into bytecode (.class files). Bytecode is a platform-independent code that can be executed on any system with a JVM.

   

2. Class Loader: The class loader loads the compiled bytecode into the JVM. It verifies the bytecode to ensure it adheres to Java's security constraints.

   

3. Bytecode Verification: The bytecode verifier checks the code fragments for illegal code that can violate access rights to objects.

   

4. Execution: The JVM interprets the bytecode or uses Just-In-Time (JIT) compilation to convert the bytecode into native machine code for execution. The JIT compiler improves performance by compiling bytecode into native code at runtime.

   

5. Garbage Collection: Java's automatic garbage collection manages memory by reclaiming memory used by objects that are no longer referenced, ensuring efficient memory management.

   

Summary

1. Compilation: .java to .class (bytecode)

2. Class Loading: Load bytecode into JVM

3. Bytecode Verification: Security checks

4. Execution: Interpretation or JIT compilation

5. Garbage Collection: Automatic memory management

Hello World Program in Java

Here is a simple "Hello, World!" program in Java:

public class HelloWorld {
    public static void main(String[] args) {
        System.out.println("Hello, World!");
    }
}

This program defines a class named HelloWorld with a main method. The main method is the entry point of the program, and it prints "Hello, World!" to the console.

Conclusion

Java has established itself as a cornerstone in the world of programming languages due to its versatility, robustness, and platform independence. From its inception in the early 1990s to its current status as a leading language for enterprise solutions, mobile applications, and web development, Java continues to evolve and adapt to the needs of developers. Its principles of simplicity, security, and high performance make it a preferred choice for both beginners and experienced programmers. With a rich set of APIs, extensive libraries, and a strong community, Java remains a powerful tool for building scalable and reliable applications. The Java tutorial page lists down all the important topics you can go through to get a deeper understanding of the language basics and advanced concepts.