This article explains Java literals. If you don’t know why float pi = 3.14 fails to compile, this article is a must read for you.

What are literals

Any value used directly in Java code is a literal. I have marked literals in the code below with bold text, so you can get a better idea what a literal is:

int num = 123; // int literal double num2 = 123.45; // double literal int result = 16 - 5; // two int literals int otherResult = result * 5; // only one literal: 5; "result" is a variable String str = "string literal"; // String literal char letter = 'a'; // char literal

Data type of a literal depends on the way it is written. In example, “abc” represents String literal, while 123 represents int literal and 123.45 represents double literal.

Java literals

In this article I want to show how to write literals that represent various Java data types.

int literals

Int literals are written as plain integer numbers.

int num1 = 123; int num2 = 123 + 456;

long literals

Long literals are written as integer numbers with L suffix.

The case of letter L doesn’t matter, but it is recommended to use uppercase L because in some fonts lowercase L looks like number 1.

long num1 = 123456789L; long num2 = 123456789l; int num3 = 123l; // compilation error - can't assign long to int

float literals

Float literals are written as floating-point numbers with F suffix. The case of letter F doesn’t matter.

float num1 = 3.14f; float num2 = 2.71F; float num3 = 123.45f + 3; // sum of float 123.45 and int 3

double literals

Double literals are written as plain floating-point numbers. Optionally suffix D (case doesn’t matter) can be provided.

double num1 = 3.14; double num2 = 2.71d; float tricky = 123.45; // fails to compile - can't assign double to float

string literals

String literals are enclosed within double quotes.

String str = "a string literal";

char literals

Char literals are enclosed within single quotes.

You can specify a character directly or as a UTF-16 code point (\u prefix and hex value).

char ch1 = 'a'; char ch2 = ' π '; // you can enter UTF-16 characters directly char ch3 = '\u03C0'; // ...or as code points, here for U+03C0 ( π)

hexadecimal literals

Hexadecimal literals are hexadecimal numbers with 0x prefix.

Those literals represent numbers in hexadecimal system (base-16).

int num = 0xFF; // num is equal to 255

binary literals

Binary literals are binary numbers with 0b prefix.

Those literals represent numbers in binary system (base-2).

int num = 0b1101; // num is equal to 13

octal literals

Octal literals are octal numbers with 0 prefix.

Those literals represent numbers in octal system (base-8).

int num = 017; // num is equal to 15

exponential notation

You can write numbers in exponential notation by using letter e to denote exponent.

Numbers in exponential notation have type of double.

double num = 1e2; // num is equal to 100.0 (1x10²)

You can write hexadecimal numbers in exponential notation by using 0x prefix and using p to denote exponent.

Exponent is written as a decimal number, and exponent base is 2.

double num = 0xFp3; // num is equal to 120.0 (15x2³)

underscores in numeric literals

Numeric literals can be formatted using underscores. The underscores in numeric literals are ignored by compiler – their only function is increase of code readability.

int num = 1_000_000; double = 1_234.56; float = 1_2_3.4_5;

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