Practice Questions — Your First Java Program

public class StudentCard {
    public static void main(String[] args) {
        System.out.println("============================");
        System.out.println("   STUDENT ID CARD");
        System.out.println("============================");
        System.out.println("Name:\t\tAnanya Desai");
        System.out.println("Age:\t\t20");
        System.out.println("College:\tNIT Trichy");
        System.out.println("Branch:\t\tCSE");
        System.out.println("CGPA:\t\t8.9");
        System.out.println("============================");
    }
}

public class Triangle {
    public static void main(String[] args) {
        System.out.println("*");
        System.out.println("**");
        System.out.println("***");
        System.out.println("****");
        System.out.println("*****");
    }
}

public class StudentReport {
    public static void main(String[] args) {
        String sep = "===================================================";
        System.out.println(sep);
        System.out.printf("%-16s| %7s | %5s | %s%n", "Name", "Roll No", "Marks", "Grade");
        System.out.println(sep);
        System.out.printf("%-16s| %7d | %5d | %3s%n", "Aarav Sharma", 1001, 87, "A");
        System.out.printf("%-16s| %7d | %5d | %3s%n", "Priya Patel", 1002, 92, "A+");
        System.out.printf("%-16s| %7d | %5d | %3s%n", "Rohan Singh", 1003, 65, "B");
        System.out.printf("%-16s| %7d | %5d | %3s%n", "Neha Gupta", 1004, 78, "B+");
        System.out.println(sep);
    }
}

public class ConcatPuzzle {
    public static void main(String[] args) {
        // a) 1 + 2 = 3 (int), then 3 + "3" = "33" (concatenation)
        System.out.println("a) " + (1 + 2 + "3"));

        // b) "1" + 2 = "12" (concat), then "12" + 3 = "123" (concat)
        System.out.println("b) " + ("1" + 2 + 3));

        // c) 1 + 2 + 3 = 6 (int), then 6 + "" = "6" (concat)
        System.out.println("c) " + (1 + 2 + 3 + ""));

        // d) "" + 1 = "1" (concat from start), "1" + 2 = "12", "12" + 3 = "123"
        System.out.println("d) " + ("" + 1 + 2 + 3));

        // e) 1 + "" = "1" (concat), "1" + 2 = "12", "12" + 3 = "123"
        System.out.println("e) " + (1 + "" + 2 + 3));

        // f) (1 + 2 + 3) = 6 (parentheses force arithmetic), then "Result: " + 6
        System.out.println("f) " + ("Result: " + (1 + 2 + 3)));
    }
}

public class Invoice {
    public static void main(String[] args) {
        System.out.println("================================================");
        System.out.println("         MODERN AGE CODERS BOOKSTORE");
        System.out.println("================================================");
        System.out.printf("%-18s %3s %8s %8s%n", "Item", "Qty", "Price", "Total");
        System.out.println("------------------------------------------------");

        double t1 = 2 * 450.00;
        double t2 = 1 * 380.00;
        double t3 = 1 * 520.00;
        double t4 = 1 * 410.00;

        System.out.printf("%-18s %3d %8.2f %8.2f%n", "Java Programming", 2, 450.00, t1);
        System.out.printf("%-18s %3d %8.2f %8.2f%n", "Data Structures", 1, 380.00, t2);
        System.out.printf("%-18s %3d %8.2f %8.2f%n", "Algorithms", 1, 520.00, t3);
        System.out.printf("%-18s %3d %8.2f %8.2f%n", "Design Patterns", 1, 410.00, t4);

        System.out.println("------------------------------------------------");
        System.out.printf("%32s %8.2f%n", "TOTAL:", t1 + t2 + t3 + t4);
        System.out.println("================================================");
    }
}

public class EscapeArt {
    public static void main(String[] args) {
        System.out.println("=== Java Learning Conversation ===");
        System.out.println();
        System.out.println("Aarav:\t\"Have you started learning Java?\"");
        System.out.println("Priya:\t\"Yes! I saved my first program at");
        System.out.println("\tC:\\Users\\Priya\\JavaProjects\\HelloWorld.java\"");
        System.out.println("Aarav:\t\"Great! Remember:");
        System.out.println("\t1. Every statement needs a semicolon");
        System.out.println("\t2. File name must match class name");
        System.out.println("\t3. main method is the entry point\"");
        System.out.println("Priya:\t\"Got it. Let's code!\"");
    }
}

public class Calculator {
    public static void main(String[] args) {
        if (args.length < 2) {
            System.out.println("Usage: java Calculator <num1> <num2>");
            System.out.println("Example: java Calculator 15 4");
            return;
        }

        int num1 = Integer.parseInt(args[0]);
        int num2 = Integer.parseInt(args[1]);

        System.out.println("Number 1: " + num1);
        System.out.println("Number 2: " + num2);
        System.out.println("Sum: " + (num1 + num2));
        System.out.println("Difference: " + (num1 - num2));
        System.out.println("Product: " + (num1 * num2));
        System.out.printf("Quotient: %.2f%n", (double) num1 / num2);
    }
}

public class CheatSheet {
    public static void main(String[] args) {
        System.out.println("========================================");
        System.out.println("   JAVA BASICS CHEAT SHEET - Chapter 3");
        System.out.println("========================================");

        System.out.println("\n--- 1. PROGRAM STRUCTURE ---");
        System.out.println("public class ClassName {");
        System.out.println("    public static void main(String[] args) {");
        System.out.println("        // Your code here");
        System.out.println("    }");
        System.out.println("}");

        System.out.println("\n--- 2. OUTPUT METHODS ---");
        System.out.println("println(x)  - prints x + newline");
        System.out.println("print(x)    - prints x (no newline)");
        System.out.println("printf(fmt) - formatted: %s %d %.2f %n");

        System.out.println("\n--- 3. COMMENTS ---");
        System.out.println("// Single-line comment");
        System.out.println("/* Multi-line comment */");
        System.out.println("/** Javadoc comment */");

        System.out.println("\n--- 4. NAMING CONVENTIONS ---");
        System.out.printf("%-12s -> %s%n", "Classes", "PascalCase (StudentRecord)");
        System.out.printf("%-12s -> %s%n", "Methods", "camelCase (calculateGpa)");
        System.out.printf("%-12s -> %s%n", "Variables", "camelCase (studentName)");
        System.out.printf("%-12s -> %s%n", "Constants", "UPPER_SNAKE (MAX_SIZE)");

        System.out.println("\n--- 5. ESCAPE SEQUENCES ---");
        System.out.printf("%-6s -> %s%n", "\\n", "Newline");
        System.out.printf("%-6s -> %s%n", "\\t", "Tab");
        System.out.printf("%-6s -> %s%n", "\\\\", "Backslash");
        System.out.printf("%-6s -> %s%n", "\\\"", "Double quote");

        System.out.println("\n========================================");
    }
}