Java Literals

A constant value in a program is denoted by a literal. Literals represent numerical (integer or floating-point), character, boolean or string values.

Example of literals:

Integer literals:
33 0 -9
Floating-point literals:
.3 0.3 3.14
Character literals:
'(' 'R' 'r' '{'
Boolean literals:(predefined values)
true false

String literals:
"language" "0.2" "r" ""

Note: Three reserved identifiers are used as predefined literals:
true and false representing boolean values.
null representing the null reference.


Let's have a closer look at our literals and type of data they can represent:

Integer Literals

Integer data types consist of the following primitive data types: int,long, byte, and short.
int is the default data type of an integer literal.
An integer literal, let's say 3000, can be specified as long by appending the suffix L (or l) to the integer value: so 3000L (or 3000l) is interpreted as a long literal.

There is no suffix to specify short and byte literals directly; 3000S , 3000B, 3000s, 3000b

Integer literals can also be specified as octal (base 8), or hexadecimal (base 16). Octal and hexadecimal have 0 and 0x prefix respectively. So 03 and 0x3 are representation of integer three in octal and hexa-decimal respectively.

Floating-point Literals

Floating-point data consist of float and double types.
The default data type of floating-point literals is double, but you can designate it explicitly by appending the D (or d) suffix. However, the suffix F (or f) is appended to designate the data type of a floating-point literal as float.

We can also specify a floating-point literal in scientific notation using Exponent (short E or e), for instance: the double literal 0.0314E2 is interpreted as
0.0314 *10² (i.e 3.14).

Examples of double literals:
0.0 0.0D 0d0.7 7D .7d
9.0 9. 9D
6.3E-2 6.3E-2D 63e-1
Examples of float literals:
0.0f 0f 7F .7f9.0f 9.F 9f
6.3E-2f 6.3E-2F 63e-1f

Note: The decimal point and the exponent are both optional and at least one digit must be specified.

Boolean Literals

As mentioned before, true and false are reserved literals representing the truth-values true and false respectively. Boolean literals fall under the primitive data type: boolean.

Character Literals

Character literals have the primitive data type character. A character is quoted in single quote (').

Note: Characters in Java are represented by the 16-bit Unicode character set.

String Literals

A string literal is a sequence of characters which has to be double-quoted (") and occur on a single line.

Examples of string literals:

"false or true"
"result = 0.01"
"a"
"Java is an artificial language"

String literals are objects of the class String, so all string literals have the type String.

Escape (aka backslash) sequences are used inside literal strings to allow print formatting as well as preventing certain characters from causing interpretation errors. Each escape sequence starts with a backslash. The available sequences are:

Seq	Usage	Seq	Usage
\b	backspace	\\	backslash
\f	formfeed	\"	double quote
\n	newline	\'	single quote
\r	carriage return	\###	Octal encoded character
\t	horizontal tab	\uHHHH	Unicode encoded character