Object Oriented Programming with Java

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Java Introduction

Java is a high-level, object-oriented programming language developed by Sun Microsystems (now owned by Oracle).

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  • It was designed to be platform-independent, secure, and simple to use. Java enables developers to write code once and run it anywhere due to its “write once, run anywhere” (WORA) capability.

Short History of Java:

  • 1991: Java project initiated by James Gosling and his team at Sun Microsystems, originally called Oak.
  • 1995: Oak was renamed to Java, and the first public version Java 1.0 was released.
  • 1998: Java 2 (J2SE) introduced improved performance and APIs.
  • 2006: Sun made Java open-source through the OpenJDK project.
  • 2010: Oracle acquired Sun Microsystems and took over Java development.
  • Present: Java continues to evolve with regular version updates (e.g., Java 8, Java 11, Java 17, Java 21, etc.).

Java Buzzwords:

These are key features and design principles of Java:

    • Simple: Easy to learn and use.
    • Object-Oriented: Based on objects and classes.
    • Distributed: Supports distributed computing using RMI and EJB.
    • Interpreted: Uses an interpreter (JVM) to execute bytecode.
    • Robust: Strong memory management and exception handling.
    • Secure: Includes security features like bytecode verification.
    • Architecture-Neutral: Can run on any platform with a JVM.
    • Portable: Code is platform-independent.
    • High Performance: Just-In-Time (JIT) compiler improves performance.
    • Multithreaded: Supports multiple threads of execution.
    • Dynamic: Adapts to evolving environments, loads classes at runtime.

    Java Virtual Machine (JVM):

    The JVM is a part of the Java Runtime Environment (JRE) that executes Java bytecode.

    • It acts as an interpreter and compiler, converting bytecode into machine code for the host system.
    • It ensures Java’s platform independence and manages memory and other resources.

      Key roles of the JVM:

      • Loads bytecode.
      • Verifies code.
      • Executes it.
      • Provides runtime environment (memory management, garbage collection, etc.).

      Java Runtime Environment (JRE):

      The JRE provides the environment required to run Java applications. It includes:

        • JVM.
        • Core Java libraries.
        • Other supporting files.

        The JRE does not include development tools like compilers. It’s meant for users who only want to run Java applications, not develop them.

        Bytecode:

        Bytecode is the intermediate code generated by the Java compiler (javac) after compiling a .java source file. The resulting .class file contains platform-independent bytecode.

          Bytecode is:

          • Executed by the JVM.
          • Platform-independent.
          • Helps achieve Java’s WORA capability.

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