java.lang

Class Float

java.lang.Object

java.lang.Number

java.lang.Float

public final class Float
extends Number

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

Since:

1.0

Author:

Paul Fisher, Andrew Haley , Eric Blake

Field Summary

Fields

Modifier and Type	Field and Description
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 Class	TYPE The primitive type float is represented by this Class object.

Constructor Summary

Constructors

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

Method Summary

Modifier and Type	Method and Description
byte	byteValue() Return the value of this Float as a byte.
static int	compare(float n1, float n2) Compare two numbers.
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.
boolean	isInfinite() Return true if the value of this Float is the same as NEGATIVE_INFINITY or POSITIVE_INFINITY, otherwise return false.
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	isNaN() Return true if the value of this Float is the same as NaN, otherwise return false.
static boolean	isNaN(float v) Return true if the float has the same value as NaN, otherwise return false.
long	longValue() Return the value of this Integer as a long.
static float	parseFloat(String s) Parse the specified String as a float.
short	shortValue() Return the value of this Float as a short.
String	toString() Convert the float value of this Float to a String.
static String	toString(float f) Convert the float to a String.
static Float	valueOf(String s) Creates a new Float object using the String.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

MAX_VALUE

public static final float MAX_VALUE

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

See Also:

Constant Field Values

MIN_VALUE

public static final float MIN_VALUE

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

See Also:

Constant Field Values

NEGATIVE_INFINITY

public static final float NEGATIVE_INFINITY

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

See Also:

Constant Field Values

POSITIVE_INFINITY

public static final float POSITIVE_INFINITY

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

See Also:

Constant Field Values

NaN

public static final float NaN

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

See Also:

Constant Field Values

TYPE

public static final Class 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

See Also:

parseFloat(String)

Method Detail

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 NumberFormat.

Parameters:

f - the float to convert

Returns:

the String representing the 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

See Also:

parseFloat(String)

parseFloat

public static float parseFloat(String s)

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 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

See Also:

MIN_VALUE, MAX_VALUE, POSITIVE_INFINITY, NEGATIVE_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

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

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

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

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.

Overrides:

toString in class Object

Returns:

the String representation

See Also:

toString(float)

byteValue

public byte byteValue()

Return the value of this Float as a byte.

Overrides:

byteValue in class Number

Returns:

the byte value

Since:

1.1

shortValue

public short shortValue()

Return the value of this Float as a short.

Overrides:

shortValue in class Number

Returns:

the short value

Since:

1.1

intValue

public int intValue()

Return the value of this Integer as an int.

Specified by:

intValue in class Number

Returns:

the int value

longValue

public long longValue()

Return the value of this Integer as a long.

Specified by:

longValue in class Number

Returns:

the long value

floatValue

public float floatValue()

Return the value of this Float.

Specified by:

floatValue in class Number

Returns:

the float value

doubleValue

public double doubleValue()

Return the value of this Float as a double

Specified by:

doubleValue in class Number

Returns:

the double value

hashCode

public int hashCode()

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

Overrides:

hashCode in class Object

Returns:

this Object's hash code

See Also:

floatToIntBits(float)

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()).

Overrides:

equals in class Object

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:

intBitsToFloat(int)

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:

intBitsToFloat(int)

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

See Also:

floatToIntBits(float), floatToRawIntBits(float)

compare

public static int compare(float n1,
                          float n2)

Compare two numbers.

Parameters:

n1 -

n2 -

Returns:

0 if n1 == n2, greater than 0 if n1 greater than n2, less than 0 if n1 less than n2.