java.lang

Class Float

Implemented Interfaces:
Comparable<T>, Serializable

public final class Float
extends Number
implements Comparable<T>

Instances of class Float represent primitive float values. Additionally, this class provides various helper functions and variables related to floats.
Since:
1.0
See Also:
Serialized Form

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
NEGATIVE_INFINITY
The value of a float representation -1.0/0.0, negative infinity.
static float
NaN
All IEEE 754 values of NaN have the same value in Java.
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
TYPE
The primitive type float is represented by this Class object.

Constructor Summary

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

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.
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 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.
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(float val)
Returns a Float object wrapping the value.
static Float
valueOf(String s)
Creates a new Float object using the String.

Methods inherited from class java.lang.Number

byteValue, doubleValue, floatValue, intValue, longValue, shortValue

Methods inherited from class java.lang.Object

clone, equals, extends Object> getClass, finalize, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Details

MAX_VALUE

public static final float MAX_VALUE
The maximum positive value a double may represent is 3.4028235e+38f.
Field Value:
2.1474836E9f

MIN_VALUE

public static final float MIN_VALUE
The minimum positive value a float may represent is 1.4e-45.
Field Value:
0.0f

NEGATIVE_INFINITY

public static final float NEGATIVE_INFINITY
The value of a float representation -1.0/0.0, negative infinity.
Field Value:
-2.1474836E9f

NaN

public static final float NaN
All IEEE 754 values of NaN have the same value in Java.
Field Value:
0.0f

POSITIVE_INFINITY

public static final float POSITIVE_INFINITY
The value of a float representation 1.0/0.0, positive infinity.
Field Value:
2.1474836E9f

SIZE

public static final int SIZE
The number of bits needed to represent a float.
Field Value:
32
Since:
1.5

TYPE

public static final Class TYPE
The primitive type float is represented by this Class object.
Since:
1.1

Constructor Details

Float

public Float(double value)
Create a Float from the primitive double specified.
Parameters:
value - the double argument

Float

public Float(float value)
Create a Float from the primitive float specified.
Parameters:
value - the float 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 Details

byteValue

public byte byteValue()
Return the value of this Float as a byte.
Overrides:
byteValue in interface Number
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

compareTo

public int compareTo(Float f)
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
Overrides:
doubleValue in interface Number
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()).

Overrides:
equals in interface 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

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

floatValue

public float floatValue()
Return the value of this Float.
Overrides:
floatValue in interface Number
Returns:
the float value

hashCode

public int hashCode()
Return a hashcode representing this Object. Float's hash code is calculated by calling floatToIntBits(floatValue()).
Overrides:
hashCode in interface Object
Returns:
this Object's hash code

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.
Overrides:
intValue in interface Number
Returns:
the int value

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

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

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

longValue

public long longValue()
Return the value of this Integer as a long.
Overrides:
longValue in interface Number
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 * 10exponent 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 str cannot be parsed as a float
NullPointerException - if str is null
Since:
1.2

shortValue

public short shortValue()
Return the value of this Float as a short.
Overrides:
shortValue in interface Number
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 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 interface Object
Returns:
the String representation

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 FloatString Representation
[+-] 0[-]0.0
Between [+-] 10-3 and 107, exclusive[-]number.number
Other numeric value[-]<digit>.<number> E[-]<number>
[+-] infinity[-]Infinity
NaNNaN
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(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

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

Float.java -- object wrapper for float Copyright (C) 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc. This file is part of GNU Classpath. GNU Classpath is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. GNU Classpath is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with GNU Classpath; see the file COPYING. If not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. Linking this library statically or dynamically with other modules is making a combined work based on this library. Thus, the terms and conditions of the GNU General Public License cover the whole combination. As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.