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Aditi Nawghare
Software Engineer at Siemens

Java String format()

Published in the Strings in Java group

What is the Java string.format() Method?

The Java string format() method is used to format strings, integers, decimal values, and so on, by using different format specifiers. This method returns the formatted string using the given locale, specified formatter, and arguments. If no locale is provided then it uses the default locale for formatting the strings. The string.format() is the static method of the Java String class. Java String format() - 1Syntax There are two types of string format() methods. One with provided locale and the other without it, which uses the default locale.

public static String format(Locale loc, String format, Object… args)
public static String format(String format, Object… args)
  1. The locale value which will be applied on format() method.
  2. Specifying the format of the output string.
  3. The number of arguments for the format string ranges from 0 to many.
Returns It always returns the formatted string according to the locale. Exceptions The format() method returns 2 exceptions.
  1. NullPointerException, if the format is null then NullPointerException is thrown.
  2. IllegalFormatException, if the specified format is illegal, or insufficient arguments are provided then this exception is thrown.

Format Specifiers

Let’s look at some commonly used specifiers.
Specifier Description
%s, %S A string formatter.
%d A decimal integer, used for integers only.
%o An octal integer, used for integers only.
%f, %F For decimal numbers, used for floating point numbers.
%x, %X A hexadecimal integer, used for integers only.
Let’s look at these specifiers with examples.

Java String.format() Method Examples

class Main {  
    public static void main(String[] args) {  
        // Integer value  
        System.out.println(String.format("%d", 234));  
        // String value  
        System.out.println(String.format("%s", "format() method")); 
        // Float value  
        System.out.println(String.format("%f", 99.99));
        // Hexadecimal value  
        System.out.println(String.format("%x", 99));
        // Char value
        System.out.println(String.format("%c", 'f'));
        // Octal value
        System.out.println(String.format("%o", 99));
234 format() method 99.990000 63 f 143

class Main {
  public static void main(String[] args) {
    int n1 = 99;
    // using two different specifiers for formatting the string
    System.out.println(String.format("%s\nhexadecimal: %x", "Result is", n1));
Result is hexadecimal: 63
Java String format() - 2Example

// to use Locale
import java.util.Locale;

class Main {
  public static void main(String[] args) {
    int number = 9999999;

    // using the default locale if none specified
    System.out.println(String.format("Number: %,d", number););

    // using the GERMAN locale as the first argument
    System.out.println(String.format(Locale.GERMAN, "Number in German: %,d", number));
Number: 9,999,999 Number in German: 9.999.999


We hope by now you understand what is Java string format() method and how to implement it for different format specifiers to get the desired results. Feel free to practice and get back whenever you need more assistance. Happy learning! To reinforce what you learned, we suggest you watch a video lesson from our Java Course
Comments (2)
matemate123 Level 50, Kraków, Poland
8 March 2023
Why so short article about so huge topic?
arunprakash Reddy Level 0, India
11 January 2023
It's always great to read such detailed blog posts like this! I like this article very much.