java.lang

Class Float

public final class Float extends Number implements Comparable<Float>

Instances of class Float represent primitive float values. Additionally, this class provides various helper functions and variables related to floats.

Since: 1.0

UNKNOWN: partly updated to 1.5

Field Summary
static float	MAX_VALUE The maximum positive value a `double` may represent is 3.4028235e+38f.
static float	MIN_VALUE The minimum positive value a `float` may represent is 1.4e-45.
static float	NaN All IEEE 754 values of NaN have the same value in Java.
static float	NEGATIVE_INFINITY The value of a float representation -1.0/0.0, negative infinity.
static float	POSITIVE_INFINITY The value of a float representation 1.0/0.0, positive infinity.
static int	SIZE The number of bits needed to represent a `float`.
static Class<Float>	TYPE The primitive type `float` is represented by this `Class` object.

Constructor Summary
	Float(float value) Create a `Float` from the primitive `float` specified.
	Float(double value) Create a `Float` from the primitive `double` specified.
	Float(String s) Create a `Float` from the specified `String`.

Method Summary
byte	byteValue() Return the value of this `Float` as a `byte`.
static int	compare(float x, float y) Behaves like `new Float(x).compareTo(new Float(y))`; in other words this compares two floats, special casing NaN and zero, without the overhead of objects.
int	compareTo(Float f) Compare two Floats numerically by comparing their `float` values.
double	doubleValue() Return the value of this `Float` as a `double`
boolean	equals(Object obj) Returns `true` if `obj` is an instance of `Float` and represents the same float value.
static int	floatToIntBits(float value) Convert the float to the IEEE 754 floating-point "single format" bit layout.
static int	floatToRawIntBits(float value) Convert the float to the IEEE 754 floating-point "single format" bit layout.
float	floatValue() Return the value of this `Float`.
int	hashCode() Return a hashcode representing this Object.
static float	intBitsToFloat(int bits) Convert the argument in IEEE 754 floating-point "single format" bit layout to the corresponding float.
int	intValue() Return the value of this `Integer` as an `int`.
static boolean	isInfinite(float v) Return `true` if the `float` has a value equal to either `NEGATIVE_INFINITY` or `POSITIVE_INFINITY`, otherwise return `false`.
boolean	isInfinite() Return `true` if the value of this `Float` is the same as `NEGATIVE_INFINITY` or `POSITIVE_INFINITY`, otherwise return `false`.
static boolean	isNaN(float v) Return `true` if the `float` has the same value as `NaN`, otherwise return `false`.
boolean	isNaN() Return `true` if the value of this `Float` is the same as `NaN`, otherwise return `false`.
long	longValue() Return the value of this `Integer` as a `long`.
static float	parseFloat(String str) Parse the specified `String` as a `float`.
short	shortValue() Return the value of this `Float` as a `short`.
static String	toHexString(float f) Convert a float value to a hexadecimal string.
static String	toString(float f) Convert the `float` to a `String`.
String	toString() Convert the `float` value of this `Float` to a `String`.
static Float	valueOf(String s) Creates a new `Float` object using the `String`.
static Float	valueOf(float val) Returns a `Float` object wrapping the value.

Field Detail

MAX_VALUE

public static final float MAX_VALUE

The maximum positive value a double may represent is 3.4028235e+38f.

MIN_VALUE

public static final float MIN_VALUE

The minimum positive value a float may represent is 1.4e-45.

NaN

public static final float NaN

All IEEE 754 values of NaN have the same value in Java.

NEGATIVE_INFINITY

public static final float NEGATIVE_INFINITY

The value of a float representation -1.0/0.0, negative infinity.

POSITIVE_INFINITY

public static final float POSITIVE_INFINITY

The value of a float representation 1.0/0.0, positive infinity.

SIZE

public static final int SIZE

The number of bits needed to represent a float.

Since: 1.5

TYPE

public static final Class<Float> TYPE

The primitive type float is represented by this Class object.

Since: 1.1

Constructor Detail

Float

public Float(float value)

Create a Float from the primitive float specified.

Parameters: value the float argument

Float

public Float(double value)

Create a Float from the primitive double specified.

Parameters: value the double argument

Float

public Float(String s)

Create a Float from the specified String. This method calls Float.parseFloat().

Parameters: s the String to convert

Throws: NumberFormatException if s cannot be parsed as a float NullPointerException if s is null

Method Detail

byteValue

public byte byteValue()

Return the value of this Float as a byte.

Returns: the byte value

Since: 1.1

compare

public static int compare(float x, float y)

Behaves like new Float(x).compareTo(new Float(y)); in other words this compares two floats, special casing NaN and zero, without the overhead of objects.

Parameters: x the first float to compare y the second float to compare

Returns: the comparison

Since: 1.4

Compare two Floats numerically by comparing their float values. The result is positive if the first is greater, negative if the second is greater, and 0 if the two are equal. However, this special cases NaN and signed zero as follows: NaN is considered greater than all other floats, including POSITIVE_INFINITY, and positive zero is considered greater than negative zero.

Parameters: f the Float to compare

Returns: the comparison

Since: 1.2

doubleValue

public double doubleValue()

Return the value of this Float as a double

Returns: the double value

equals

public boolean equals(Object obj)

Returns true if obj is an instance of Float and represents the same float value. Unlike comparing two floats with ==, this treats two instances of Float.NaN as equal, but treats 0.0 and -0.0 as unequal.

Note that f1.equals(f2) is identical to floatToIntBits(f1.floatValue()) == floatToIntBits(f2.floatValue()).

Parameters: obj the object to compare

Returns: whether the objects are semantically equal

floatToIntBits

public static int floatToIntBits(float value)

Convert the float to the IEEE 754 floating-point "single format" bit layout. Bit 31 (the most significant) is the sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and bits 22-0 (masked by 0x007fffff) are the mantissa. This function collapses all versions of NaN to 0x7fc00000. The result of this function can be used as the argument to Float.intBitsToFloat(int) to obtain the original float value.

Parameters: value the float to convert

Returns: the bits of the float

See Also: Float

floatToRawIntBits

public static int floatToRawIntBits(float value)

Convert the float to the IEEE 754 floating-point "single format" bit layout. Bit 31 (the most significant) is the sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves NaN alone, rather than collapsing to a canonical value. The result of this function can be used as the argument to Float.intBitsToFloat(int) to obtain the original float value.

Parameters: value the float to convert

Returns: the bits of the float

See Also: Float

floatValue

public float floatValue()

Return the value of this Float.

Returns: the float value

hashCode

public int hashCode()

Return a hashcode representing this Object. Float's hash code is calculated by calling floatToIntBits(floatValue()).

Returns: this Object's hash code

See Also: Float

intBitsToFloat

public static float intBitsToFloat(int bits)

Convert the argument in IEEE 754 floating-point "single format" bit layout to the corresponding float. Bit 31 (the most significant) is the sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves NaN alone, so that you can recover the bit pattern with Float.floatToRawIntBits(float).

Parameters: bits the bits to convert

Returns: the float represented by the bits

intValue

public int intValue()

Return the value of this Integer as an int.

Returns: the int value

isInfinite

public static boolean isInfinite(float v)

Return true if the float has a value equal to either NEGATIVE_INFINITY or POSITIVE_INFINITY, otherwise return false.

Parameters: v the float to compare

Returns: whether the argument is (-/+) infinity

isInfinite

public boolean isInfinite()

Return true if the value of this Float is the same as NEGATIVE_INFINITY or POSITIVE_INFINITY, otherwise return false.

Returns: whether this Float is (-/+) infinity

isNaN

public static boolean isNaN(float v)

Return true if the float has the same value as NaN, otherwise return false.

Parameters: v the float to compare

Returns: whether the argument is NaN

isNaN

public boolean isNaN()

Return true if the value of this Float is the same as NaN, otherwise return false.

Returns: whether this Float is NaN

longValue

public long longValue()

Return the value of this Integer as a long.

Returns: the long value

parseFloat

public static float parseFloat(String str)

Parse the specified String as a float. The extended BNF grammar is as follows:

 DecodableString:
      ( [ - | + ] NaN )
    | ( [ - | + ] Infinity )
    | ( [ - | + ] FloatingPoint
              [ f | F | d
                | D] )
 FloatingPoint:
      ( { Digit }+ [ . { Digit } ]
              [ Exponent ] )
    | ( . { Digit }+ [ Exponent ] )
 Exponent:
      ( ( e | E )
              [ - | + ] { Digit }+ )
 Digit: '0' through '9'

NaN and infinity are special cases, to allow parsing of the output of toString. Otherwise, the result is determined by calculating n * 10^exponent to infinite precision, then rounding to the nearest float. Remember that many numbers cannot be precisely represented in floating point. In case of overflow, infinity is used, and in case of underflow, signed zero is used. Unlike Integer.parseInt, this does not accept Unicode digits outside the ASCII range.

If an unexpected character is found in the String, a NumberFormatException will be thrown. Leading and trailing 'whitespace' is ignored via String.trim(), but spaces internal to the actual number are not allowed.

To parse numbers according to another format, consider using {@link java.text.NumberFormat}.

Parameters: str the String to convert

Returns: the float value of s

Throws: NumberFormatException if s cannot be parsed as a float NullPointerException if s is null

Since: 1.2

UNKNOWN: specify where/how we are not in accord with the spec.

shortValue

public short shortValue()

Return the value of this Float as a short.

Returns: the short value

Since: 1.1

toHexString

public static String toHexString(float f)

Convert a float value to a hexadecimal string. This converts as follows:

A NaN value is converted to the string "NaN".
Positive infinity is converted to the string "Infinity".
Negative infinity is converted to the string "-Infinity".
For all other values, the first character of the result is '-' if the value is negative. This is followed by '0x1.' if the value is normal, and '0x0.' if the value is denormal. This is then followed by a (lower-case) hexadecimal representation of the mantissa, with leading zeros as required for denormal values. The next character is a 'p', and this is followed by a decimal representation of the unbiased exponent.

Parameters: f the float value

Returns: the hexadecimal string representation

Since: 1.5

toString

public static String toString(float f)

Convert the float to a String. Floating-point string representation is fairly complex: here is a rundown of the possible values. "[-]" indicates that a negative sign will be printed if the value (or exponent) is negative. "<number>" means a string of digits ('0' to '9'). "<digit>" means a single digit ('0' to '9').

Value of Float	String Representation
[+-] 0	`[-]0.0`
Between [+-] 10^-3 and 10⁷, exclusive	`[-]number.number`
Other numeric value	`[-]<digit>.<number> E[-]<number>`
[+-] infinity	`[-]Infinity`
NaN	`NaN`

Yes, negative zero is a possible value. Note that there is always a . and at least one digit printed after it: even if the number is 3, it will be printed as 3.0. After the ".", all digits will be printed except trailing zeros. The result is rounded to the shortest decimal number which will parse back to the same float.

To create other output formats, use {@link java.text.NumberFormat}.

Parameters: f the float to convert

Returns: the String representing the float

UNKNOWN: specify where we are not in accord with the spec.

toString

public String toString()

Convert the float value of this Float to a String. This method calls Float.toString(float) to do its dirty work.

Returns: the String representation

See Also: Float

valueOf

public static Float valueOf(String s)

Creates a new Float object using the String.

Parameters: s the String to convert

Returns: the new Float

Throws: NumberFormatException if s cannot be parsed as a float NullPointerException if s is null

valueOf

public static Float valueOf(float val)

Returns a Float object wrapping the value. In contrast to the Float constructor, this method may cache some values. It is used by boxing conversion.

Parameters: val the value to wrap

Returns: the Float

Since: 1.5