Formatted Printing with System.out.printf & Format Specifiers

1Concept

System.out.printf() writes formatted strings to the console using format specifiers like %d (decimal int), %s (string), %f (float/double), %c (char), %b (boolean), and %n (platform-independent newline). Width flags and precision controls allow clean tabular outputs.

2Architecture Diagram

Format String: "| %-15s | %10.2f | %4d |%n"
                      |           |      |
                 Left-align    2 Decimals 4-digit width

3Code Example

public class PrintfDemo {
    public static void main(String[] args) {
        System.out.println("+-----------------+------------+------+");
        System.out.println("| PRODUCT         | PRICE ($)  | QTY  |");
        System.out.println("+-----------------+------------+------+");

        String item1 = "Cloud Server";
        double price1 = 129.95;
        int qty1 = 4;
        System.out.printf("| %-15s | %10.2f | %4d |%n", item1, price1, qty1);

        String item2 = "PostgreSQL DB";
        double price2 = 249.50;
        int qty2 = 2;
        System.out.printf("| %-15s | %10.2f | %4d |%n", item2, price2, qty2);
        System.out.println("+-----------------+------------+------+");
    }
}

4Expected Output

+-----------------+------------+------+
| PRODUCT         | PRICE ($)  | QTY  |
+-----------------+------------+------+
| Cloud Server    |     129.95 |    4 |
| PostgreSQL DB   |     249.50 |    2 |
+-----------------+------------+------+

5Key Takeaways

• ✓Always use %n instead of \n in printf for cross-platform newline compatibility (Windows uses \r\n, Linux uses \n).
• ✓String.format() uses identical format syntax but returns a String instead of writing to console.
• ✓Negative width flag (e.g. %-15s) left-aligns text; positive right-aligns.