Java String format() Method

❮ String Methods

String myStr = "Hello %s! One kilobyte is %,d bytes.";
String result = String.format(myStr, "World", 1024);
System.out.println(result);

Definition and Usage

The format() method returns a formatted string using a locale, format and additional arguments.

If a locale is not passed to this method then the locale given by Locale.getDefault() is used.

Data from the additional arguments is formatted and written into placeholders in the format string, which are marked by a % symbol. The way in which arguments are formatted depends on the sequence of characters that follows the % symbol.

Placeholders

The placeholders have the form %[arg$][flags][width][.precision]conversion. The components in [square brackets] are optional.

An explanation of each of the components:

• arg$ - Optional. A number followed by a $ sign which indicates which of the additional arguments to use, argument numbers start at 1. This can be replaced with a < which specifies that the argument from the previous placeholder should be used.
• flags - Optional. A sequence of any of the following characters:
  • - - Makes the output left-justified by adding any padding spaces to the right instead of to the left.
  • # - Shows an alternate representation of the formatted data depending on the conversion.
  • + - Causes positive numbers to always be prefixed with "+".
  • - (A space character) This prefixes a space to positive numbers, primarily so that the digits can be lined up with the digits of negative numbers.
  • 0 - Pads numbers with zeroes on the left.
  • , - Groups digits (for example by thousands) and puts separators between the groups. This is affected by the locale.
  • ( - Encloses negative numbers in parentheses.
• width - Optional. A whole number specifying the minimum number of characters that the output should occupy. If necessary spaces are added to the right to reach this number, or to the left if the - flag is used.
• .precision Optional. A . followed by a whole number indicating how many decimal digits to show in the formatted data.
• conversion - Required. A character which indicates how an argument's data should be represented. If the character is uppercase the data will be formatted in uppercase where possible. The list of possible characters is shown in the table below.

List of conversions

Syntax

One of the following:

public static String format(Locale locale, String format, Object... args)

public static String format(String format, Object... args)

Parameter Values

Technical Details

More Examples

String result = String.format("%2$,3.2f %1$s", "meters", 1260.5052);
System.out.println(result);

String result = String.format("%3$c %2$c %1$c", 'a', 'b', 'c');
System.out.println(result);

double myNumber = 123456.78;
String result;

// Default
result = String.format("%f", myNumber);
System.out.println(result);

// Two decimal digits
result = String.format("%.2f", myNumber);
System.out.println(result);

// No decimal digits
result = String.format("%.0f", myNumber);
System.out.println(result);

// No decimal digits but keep the decimal point
result = String.format("%#.0f", myNumber);
System.out.println(result);

// Group digits
result = String.format("%,.2f", myNumber);
System.out.println(result);

// Scientific notation with two digits of precision
result = String.format("%.2e", myNumber);
System.out.println(result);

long date = 1711638903488L; // Unix timestamp (number of milliseconds since January 1, 1970)
String result

// Time
result = String.format("%tl:%<tM %<tp", date);
System.out.println(result);

// Month and day
result = String.format("%tB %<te", date);
System.out.println(result);

// Full date representation
result = String.format("%tc", date);
System.out.println(result);

String result;

// Represent characters from their unicode code points
result = String.format("%c%c%c%c%c", 72, 101, 108, 108, 111);
System.out.println(result);

// Force unicode characters to uppercase
result = String.format("%C%C%C%C%C", 72, 101, 108, 108, 111);
System.out.println(result);