Java — Reference Types, Strings, Constants & Variable Scopes

public class Main {
    
    // 1. Static Variable (Class-level scope, shared by everyone)
    public static final String UNIVERSITY_NAME = "Osmania University";
    public static int totalEnrolledStudents    = 0;

    // 2. Instance Variables (Object-level scope in Heap)
    private String studentName;
    private double gpa;

    // Constructor to initialize instance variables
    public Main(String name, double gpa) {
        this.studentName = name;
        this.gpa = gpa;
        totalEnrolledStudents++; // Increment shared class counter
    }

    public void displayStudent() {
        // 3. Local Variable (Method-level scope in Stack)
        String status = (this.gpa >= 3.5) ? "Distinction" : "Standard Pass";

        System.out.println("University : " + UNIVERSITY_NAME);
        System.out.println("Student    : " + this.studentName);
        System.out.println("GPA        : " + this.gpa + " (" + status + ")");
        System.out.println("----------------------------------------");
    }

    public static void main(String[] args) {
        // Creating student object instances
        Main s1 = new Main("Balaji Nayak", 3.9);
        Main s2 = new Main("Ravi Teja", 3.2);

        s1.displayStudent();
        s2.displayStudent();

        System.out.println("Total Students Enrolled: " + Main.totalEnrolledStudents);
    }
}

University : Osmania University
Student    : Balaji Nayak
GPA        : 3.9 (Distinction)
----------------------------------------
University : Osmania University
Student    : Ravi Teja
GPA        : 3.2 (Standard Pass)
----------------------------------------
Total Students Enrolled: 2

public class StringPoolInspection {
    public static void main(String[] args) {
        // String Literals (Stored in String Constant Pool)
        String str1 = "Java2026";
        String str2 = "Java2026";

        // String Object using 'new' (Forces separate Heap allocation)
        String str3 = new String("Java2026");

        System.out.println("=== String Pool Memory Comparison ===");
        // == compares memory reference pointers
        System.out.println("str1 == str2 (Pool Memory Reference): " + (str1 == str2)); // true!
        System.out.println("str1 == str3 (Heap Object Reference): " + (str1 == str3)); // false!

        // .equals() compares actual character content
        System.out.println("str1.equals(str3) (Content Check)   : " + str1.equals(str3)); // true!
    }
}