How to Use printf in Java: Syntax and Examples

In Java, printf is used to print formatted text to the console. You use it by calling System.out.printf with a format string and optional arguments to insert values in a specific format.

Syntax

The basic syntax of printf in Java is:

• System.out.printf(format, args...);

Here, format is a string that contains text and format specifiers like %d for integers or %s for strings. The args are the values to insert into the format string.

java

System.out.printf("format string", arguments);

Example

This example shows how to print a formatted message with a string and an integer using printf. It demonstrates inserting values into the format string.

java

public class PrintfExample {
    public static void main(String[] args) {
        String name = "Alice";
        int age = 30;
        System.out.printf("%s is %d years old.%n", name, age);
    }
}

Output

Alice is 30 years old.

Common Pitfalls

Common mistakes when using printf include:

• Not matching the number of format specifiers with the number of arguments.
• Using the wrong format specifier for the data type (e.g., %d for a string).
• Forgetting to include \n or %n for a new line if needed.

These cause runtime errors or incorrect output.

java

public class PrintfMistake {
    public static void main(String[] args) {
        String name = "Bob";
        // Wrong: missing argument for %d
        // System.out.printf("Name: %s, Age: %d\n", name);

        // Correct:
        int age = 25;
        System.out.printf("Name: %s, Age: %d\n", name, age);
    }
}

Output

Name: Bob, Age: 25

Quick Reference

Format Specifier	Description	Example
%d	Decimal integer	42
%s	String	"hello"
%f	Floating-point number	3.14
%c	Character	'A'
%n	Platform-specific newline	(new line)
%%	Literal percent sign	%

Key Takeaways

Use System.out.printf with a format string and matching arguments for formatted output.

Match format specifiers like %d, %s, %f to the correct data types.

Always ensure the number of specifiers matches the number of arguments.

Include \n or %n for new lines to keep output readable.

Common errors come from mismatched specifiers or missing arguments.