Java Programming Unit 1

Introduction to Java

• Java is a high-level, object-oriented programming language aimed at portability, simplicity, and security.
• Created by James Gosling at Sun Microsystems in the mid-1990s; now owned by Oracle Corporation.
• Java’s main feature is platform independence, enabling code to run on any system with a Java Virtual Machine (JVM).
• Its object-oriented programming (OOP) model facilitates the creation of reusable code, improving maintenance.
• Strong type checking in Java minimizes common programming errors.
• Java is widely used for enterprise applications, web applications, mobile apps, and games.
• To start programming in Java, download the Java Development Kit (JDK) from Oracle’s website and use an IDE like Eclipse, IntelliJ IDEA, or NetBeans.

Features of Java

• Platform Independence: Java is compiled into bytecode that is executable on any system with a JVM, supporting distributed applications.
• Compiled and Interpreted: Java source code is compiled into binary bytecode, which is then interpreted by the JVM.

Java Virtual Machine (JVM) and Bytecode

• The JVM executes Java bytecode, translating it into machine language for the processor.
• Java bytecode is optimized for performance and is platform-independent.
• It includes optimizations like constant folding, dead code elimination, and method in-lining.
• JVM features include memory management, garbage collection, and security, along with a just-in-time (JIT) compiler for dynamic compilation of frequently used bytecode.

Types of Java Programs

• OOP promotes modular programming, organizing code into objects and classes, enhancing reuse and maintenance.
• OOP offers better scalability compared to procedural-oriented programming (POP).

Basic Java Program Structure

• Example program:

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

• Components of the program:
  • public: Access modifier making the class/method accessible.
  • class: Keyword to define a class.
  • HelloWorld: Class name.
  • main: The entry point of the program, executed on runtime.
  • (String[] args): Argument list for command-line input.
  • System.out.println: Method to print output to the console.

Basic Data Types in Java

• Primitive types include:
  • byte: 8-bit signed integer (-128 to 127).
  • short: 16-bit signed integer (-32,768 to 32,767).
  • int: 32-bit signed integer (-2,147,483,648 to 2,147,483,647).
  • long: 64-bit signed integer (-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807).
  • float: 32-bit floating-point number with ~7 decimal digits precision.
  • double: 64-bit floating-point number with ~15 decimal digits precision.
  • boolean: Represents true or false values.
  • char: Represents a single character in Unicode.

Reference Data Types

• Classes: Blueprints for creating objects, containing fields and methods.
  • Example class:

    public class Person {
        private String name;
        private int age;
    
        public Person(String name, int age) {
            this.name = name;
            this.age = age;
        }
    
        public String getName() {
            return name;
        }
    
        public int getAge() {
            return age;
        }
    }
    

• Interfaces: Define a contract of behaviors for classes to implement.
  • Example interface:

    public interface Drawable {
        public void draw();
    }
    

• Arrays: Collections of elements of the same data type, stored in contiguous memory.
  • Example of an integer array:

    int[] numbers = {1, 2, 3, 4, 5};
    

Operators in Java

• Operators are symbols that perform operations on operands, categorized as:
  • Arithmetic operators: For operations on numerical values.

Explore the fundamentals of Java programming in this quiz. Learn about the introduction to Java, its features, and its significance as a high-level, object-oriented programming language. Test your knowledge on key concepts and the history behind Java's creation.