
Integer Literals
An integer literal is of type long
if it ends with the letter 'L' or 'l'; otherwise it is
of type int
. It is recommended that you use the upper case letter 'L' because the lower
case letter 'l' is hard to distinguish from the digit 1.
Values of the integral types byte
, short
, int
, and
long
can be created from int
literals. Values of type
long
that exceed the range of int
can be created from long
literals. Integer literals can be expressed these number systems:
Decimal: Base 10, whose digits consists of the numbers 0 through 9; this is the number system you use every day
Hexadecimal: Base 16, whose digits consist of the numbers 0 through 9 and the letters A through F
Binary: Base 2, whose digits consists of the numbers 0 and 1 (you can create binary literals in Java SE 7 and later)
For generalpurpose programming, the decimal system is likely to be the only number system you will ever use. However, if you need to use another number system, the following example shows the correct syntax. The prefix '0x' indicates hexadecimal and '0b' indicates binary:
int decVal = 26; // The number 26, in decimal int hexVal = 0x1a; // The number 26, in hexadecimal int binVal = 0b11010; // The number 26, in binary
Binary Literals
In Java SE 7, the integral types (byte
, short
, int
, and
long
) can also be expressed using the binary number system. To specify a binary
literal, add the prefix 0b
or 0B
to the number. The following examples
show binary literals:
// An 8bit 'byte' value: byte aByte = 0b00100001; // A 16bit 'short' value: short aShort = 0b0010001010001010; // Some 32bit 'int' values: int anInt1 = 0b10100001010001011010000101000101; int anInt2 = 0b101; int anInt3 = 0B101; // The B can be upper or lower case. // A 64bit 'long' value. Note the "L" suffix: long aLong = 0b1010000101000101101000010100010110100001010001011010000101000101L; // OK, implicit casting int to float or double variable float f1 = 0b0001; double d1 = 0b0001; // COMPILATION FAILS! Binary literal can only be of integer type (byte, char, int, long), // while 'd' or 'f' suffixes explicitly say these are decimal point type literals double d2 = 0b0001d; float f2 = 0b0001f;
Underscores in Numeric Literals
In Java SE 7 and later, any number of underscore characters (_) can appear anywhere between digits in a numerical literal. This feature enables you, for example, to separate groups of digits in numeric literals, which can improve the readability of your code.
For instance, if your code contains numbers with many digits, you can use an underscore character to separate digits in groups of three, similar to how you would use a punctuation mark like a comma, or a space, as a separator.
The following example shows other ways you can use the underscore in numeric literals:
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;
You can place underscores only between digits; you CANNOT place underscores in the following places:
At the beginning or end of a number
Adjacent to a decimal point in a floating point literal
Prior to an 'F' or 'L' suffix
In positions where a string of digits is expected
The following examples demonstrate valid and invalid underscore placements in numeric literals.
Valid:
int x1 = 5_2; // OK (decimal literal) int x2 = 5_______2; // OK (decimal literal) int x3 = 0x5_2; // OK (hexadecimal literal) int x4 = 0B0_0_0; // OK (binary literal)
Invalid:
float pi1 = 3_.1415F; // Cannot put underscores adjacent to a decimal point float pi2 = 3._1415F; // Cannot put underscores adjacent to a decimal point long ssn = 999_99_9999_L; // Cannot put underscores prior to an L suffix int x1 = 52_; // Cannot put underscores at the end of a literal int x2 = 0_x52; // Cannot put underscores in the 0x radix prefix int x3 = 0x_52; // Cannot put underscores at the beginning of a number int x4 = 0x52_; // Cannot put underscores at the end of a number
Invalid (compilable, but logical error):
int x1 = _52; // This is an identifier, not a numeric literal