3.10.2 Floating-Point Literals

See §4.2.3 for a general discussion of the floating-point types and values.

A floating-point literal has the following parts: a whole-number part, a decimal point (represented by an ASCII period character), a fractional part, an exponent, and a type suffix. The exponent, if present, is indicated by the ASCII letter e or E followed by an optionally signed integer.

At least one digit, in either the whole number or the fraction part, and either a decimal point, an exponent, or a float type suffix are required. All other parts are optional.

A floating-point literal is of type float if it is suffixed with an ASCII letter F or f; otherwise its type is double and it can optionally be suffixed with an ASCII letter D or d.

FloatingPointLiteral:

	Digits . Digitsopt ExponentPartopt FloatTypeSuffixopt

	. Digits ExponentPartopt FloatTypeSuffixopt

	Digits ExponentPart FloatTypeSuffixopt

	Digits ExponentPartopt FloatTypeSuffix

ExponentPart:

	ExponentIndicator SignedInteger

ExponentIndicator: one of

	e E

SignedInteger:

	Signopt Digits

Sign: one of

	+ -

FloatTypeSuffix: one of

	f F d D

The Java types float and double are IEEE 754 32-bit single-precision and 64-bit double-precision binary floating-point values, respectively.

The details of proper input conversion from a Unicode string representation of a floating-point number to the internal IEEE 754 binary floating-point representation are described for the methods valueOf of class Float (§20.9.17) and class Double (§20.10.16) of the package java.lang.

The largest positive finite float literal is 3.40282347e+38f. The smallest positive finite nonzero literal of type float is 1.40239846e-45f. The largest positive finite double literal is 1.79769313486231570e+308. The smallest positive finite nonzero literal of type double is 4.94065645841246544e-324.

See Float.MIN_VALUE (§20.9.1) and Float.MAX_VALUE (§20.9.2); see also Double.MIN_VALUE (§20.10.1) and Double.MAX_VALUE (§20.10.2).

A compile-time error occurs if a nonzero floating-point literal is too large, so that on rounded conversion to its internal representation it becomes an IEEE 754 infinity. A Java program can represent infinities without producing a compile-time error by using constant expressions such as 1f/0f or -1d/0d or by using the predefined constants POSITIVE_INFINITY and NEGATIVE_INFINITY of the classes Float (§20.9) and Double (§20.10).

A compile-time error occurs if a nonzero floating-point literal is too small, so that, on rounded conversion to its internal representation, it becomes a zero. A compile-time error does not occur if a nonzero floating-point literal has a small value that, on rounded conversion to its internal representation, becomes a nonzero denormalized number.

Predefined constants representing Not-a-Number values are defined in the classes Float and Double as Float.NaN (§20.9.5) and Double.NaN (§20.10.5).

Examples of float literals:

	1e1f			2.f			.3f		0f		3.14f			6.022137e+23f

Examples of double literals:

	1e1			2.			.3		0.0		3.14			1e-9d		1e137

There is no provision for expressing floating-point literals in other than decimal radix. However, method intBitsToFloat (§20.9.23) of class Float and method longBitsToDouble (§20.10.22) of class Double provide a way to express floating-point values in terms of hexadecimal or octal integer literals. For example, the value of:

Double.longBitsToDouble(0x400921FB54442D18L)

is equal to the value of Math.PI (§20.11.2).