Format Specifier in java

What is a Format Specifier?

A format specifier is a special symbol used inside System.out.printf() or String.format() to control how values are printed.

It starts with a % sign, followed by a character or number that tells Java what type of value to print and how to format it.

Example

System.out.printf("My age is %d and my name is %s", 20, "Saraswathi");

output
My age is 20 and my name is Saraswathi

Here:
%d → integer (age)
%s → string (name)

Common Format Specifiers

• %d → for all integer types (byte, short, int, long)

• %f → for floating-point numbers (float, double)

• %c→ for characters

• %b → for booleans

• %s → for strings

Special Characters (Escape Sequences)

• \n -> moves to next line

• \t -> adds horizontal space

• %n -> newline

Formatting Options

You can control width, alignment, and precision:

%5d Print integer in a field of width 5 (right-aligned) ' 25'

%-5d Print integer in width 5 (left-aligned) '25 '

%05d Print integer padded with zeros '00025'

%.2f Print float with 2 digits after decimal 3.14

%10.2f Total width = 10, 2 digits after decimal ' 3.14'

example

public class FormatDemo {
    public static void main(String[] args) {
        int age = 22;
        float mark = 95.678f;
        char grade = 'A';
        String name = "Saraswathi";
        boolean pass = true;

        System.out.printf("Name: %-10s Age: %2d  Marks: %.2f  Grade: %c  Pass: %b%n",
                          name, age, mark, grade, pass);
    }
}

output
Name: Saraswathi Age: 22 Marks: 95.68 Grade: A Pass: true