Java Fundamentals & Syntax

Duration: 7.0 min

Java Fundamentals & Syntax

Java is a powerful, object-oriented programming language that runs on the Java Virtual Machine (JVM). This makes it platform-independent - write once, run anywhere. Java is widely used in enterprise applications, Android development, and large-scale systems. Understanding Java fundamentals is essential for becoming a professional developer. The JVM handles memory management, garbage collection, and provides security features that make Java robust and reliable for production systems.

JVM, JDK, and JRE

The Java ecosystem consists of three key components: JVM (Java Virtual Machine) executes bytecode, JRE (Java Runtime Environment) provides libraries and JVM, and JDK (Java Development Kit) includes compiler and tools. Understanding these distinctions is crucial for Java development. The JVM is what makes Java platform-independent - it abstracts away OS-specific details. The JDK is what you need for development, while JRE is sufficient for running Java applications.

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

Hello, World!

public class Variables {
    public static void main(String[] args) {
        int age = 25;
        String name = "Alice";
        double salary = 50000.50;
        System.out.println("Name: " + name);
        System.out.println("Age: " + age);
        System.out.println("Salary: " + salary);
    }
}

Name: Alice
Age: 25
Salary: 50000.5

public class DataTypes {
    public static void main(String[] args) {
        byte b = 127;
        short s = 32000;
        int i = 2147483647;
        long l = 9223372036854775807L;
        float f = 3.14f;
        double d = 3.141592653589793;
        char c = 'A';
        boolean bool = true;
        System.out.println("All data types initialized");
    }
}

All data types initialized

public class TypeCasting {
    public static void main(String[] args) {
        int intValue = 100;
        long longValue = intValue;
        double doubleValue = 99.99;
        int intFromDouble = (int) doubleValue;
        System.out.println("Int to Long: " + longValue);
        System.out.println("Double to Int: " + intFromDouble);
    }
}

Int to Long: 100
Double to Int: 99

public class Comments {
    // Single line comment
    public static void main(String[] args) {
        /* Multi-line comment
           explaining the code */
        System.out.println("Comments example");
    }
}

Comments example

public class Operators {
    public static void main(String[] args) {
        int a = 10, b = 5;
        System.out.println("Addition: " + (a + b));
        System.out.println("Subtraction: " + (a - b));
        System.out.println("Multiplication: " + (a * b));
        System.out.println("Division: " + (a / b));
        System.out.println("Modulus: " + (a % b));
    }
}

Addition: 15
Subtraction: 5
Multiplication: 50
Division: 2
Modulus: 0

public class Comparison {
    public static void main(String[] args) {
        int x = 10, y = 20;
        System.out.println("x == y: " + (x == y));
        System.out.println("x != y: " + (x != y));
        System.out.println("x > y: " + (x > y));
        System.out.println("x < y: " + (x < y));
    }
}

x == y: false
x != y: true
x > y: false
x < y: true

public class Logical {
    public static void main(String[] args) {
        boolean a = true, b = false;
        System.out.println("a && b: " + (a && b));
        System.out.println("a || b: " + (a || b));
        System.out.println("!a: " + (!a));
    }
}

a && b: false
a || b: true
!a: false

💡 Tip: Best Practice: Always use meaningful variable names and follow Java naming conventions (camelCase for variables, PascalCase for classes).

💡 Tip: Common Mistake: Forgetting semicolons at the end of statements. Every statement in Java must end with a semicolon.

Learn more: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/