How to format a Java int or long with printf example

How use Java printf to format int values

It’s much easier to format an int with printf than a float or double, because decimal precision is not a concern.

To use Java’s printf to format an int, long, short or byte value, follow these rules:

1. Use %d as the placeholder specifier.
2. Precede the letter d with a comma to add a thousands group separator.
3. Add additional parameters to left or right justify, add a plus sign, or zero pad.

Java int printf example

Here is a simple example of both an int and a long formatted with Java’s printf function:

package com.mcnz.rps;

public class JavaPrintfIntExample {
  /* Java printf int code example. */
  public static void main(String[] args) {
    int eresting = 54321;
    long johns   = 98765L;
    System.out.printf("%,d :: %d", eresting, johns);
    /* Printf int example prints: 54,321 :: 98765 */
  }
}

Java int printf function explained

There are two key takeaways from this Java int printf example:

• The %d specifier works for long, int, double and short datatypes.
• The inclusion of a comma adds a grouping separator for large numbers.

Be careful not to confuse the %d and %f specifiers. The %d specifier is used for integer types, while %f is only used with a Java float or double.

Java integer printf syntax

The full format for the Java printf function when used with an int is as follows:

% [flags] [width] specifier-character

Advanced Java in printf code example

Here is a more advanced application of the various flags, options and specifiers that you can use with printf and integer values:

package com.mcnz.rps;

public class JavaPrintfIntExample {
  /* Java printf int code example. */
  public static void main(String[] args) {
    int eresting = 54321;
    long johns   = 98765L;
    System.out.printf("%0,10d :: %+,7d", eresting, johns);
    /* Printf int example prints: 000054,321 :: +98,765 */
  }
}

Table of Java integer printf patterns

Here’s some sample code to generate a chart of different integer printf patterns in Java:

System.out.printf("------------------------------%n");
System.out.printf(" Java int printf chart%n");
System.out.printf(" (number: 123457890)%n");
System.out.printf("------------------------------%n");
System.out.printf("| %-8s | %s |%n", "PATTERN", "RESULT");
System.out.printf("------------------------------%n");
System.out.printf("| %-8s | %d |%n",      "%d",      123457890);
System.out.printf("| %-8s | %,d |%n",     "%,d",     123457890);
System.out.printf("| %-8s | %,15d |%n",   "%,15d",   123457890); 
System.out.printf("| %-8s | %+,15d |%n",  "%+,15d",  123457890);
System.out.printf("| %-8s | %-+,15d |%n", "%-+,15d", 123457890);
System.out.printf("| %-8s | %0,15d |%n",  "%0,15d",  123457890);

Sometimes it’s fun to format output with a Java printf chart.

Example code on how to format Java integer and long values with printf.