Underscores in Numeric Literals

In Java SE 7, any number of underscore characters (_) can appear anywhere between digits in a numerical literal.

This feature is used to separate groups of digits in numeric literals, which can improve the readability of your code.

Example:

long creditCardNumber = 1234_5678_9012_3456L;

long socialSecurityNumber = 999_99_9999L;

float pi =      3.14_15F;

long hexBytes = 0xFF_EC_DE_5E;

long hexWords = 0xCAFE_BABE;

long maxLong = 0x7fff_ffff_ffff_ffffL;

byte nybbles = 0b0010_0101;

long bytes = 0b11010010_01101001_10010100_10010010;

Important points:

We cannot place underscores in the following places:

1. At the beginning or end of a number

2. Adjacent to a decimal point in a floating point literal

3. Prior to an F or L suffix

4. In positions where a string of digits is expected.

Invalid Examples:

float pi1 = 3_.1415F;

float pi2 = 3._1415F;

long id = 999_99_9999_L;

int num = _42;

int num = 0_x54;

int num = 0x_52;

int num = 0x52_;

int num = 052_;

Valid Examples:

int num = 5_2;

int num = 5_______2;

int num = 0x5_2;

int num = 0_52; (octal literal) 

Example:

public class UnderscoresNumbers {

     public static void main(String[] args) {

           int a = 10_597;

           int b = 1_11_597;

          

           int sum = a+b;

          

           System.out.println("Sum is: "+ sum);

     }

}

Output:

     Sum is: 122194