Java Basic Notes
Java is one of the most popular programming languages in the world. It was developed by Sun Microsystems and is
now maintained by Oracle. Java is widely used for web applications, desktop applications, mobile applications,
enterprise software, and cloud-based systems. Java follows the principle of โWrite Once, Run Anywhereโ because
Java programs can run on any platform that contains the Java Virtual Machine (JVM).
1. Features of Java
โขPlatform Independent โ Java programs can run on different operating systems.
โขObject-Oriented โ Java uses classes and objects.
โขSecure โ Java provides security through bytecode verification and exception handling.
โขRobust โ Strong memory management and error handling.
โขMultithreaded โ Multiple tasks can run simultaneously.
โขPortable โ Java programs can easily move between platforms.
2. JDK, JRE, and JVM
JDK (Java Development Kit) is used for developing Java programs. It contains the compiler, debugger, and JRE.
JRE (Java Runtime Environment) is used to run Java applications. It contains JVM and supporting files. JVM (Java
Virtual Machine) converts Java bytecode into machine code and executes it.
3. Structure of a Java Program
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello World");
}
}
class โ Defines a class.
main() โ Entry point of the Java program.
System.out.println() โ Used to print output.
4. Data Types in Java
Data Type Description
int Stores integers
float Stores decimal numbers
double Stores large decimal numbers
char Stores single character
boolean Stores true or false values
String Stores text
