Float

public final class Float extends Number
implements Comparable<Float>

The Float class wraps a value of primitive type float in an object. An object of type Float contains a single field whose type is float.

In addition, this class provides several methods for converting a float to a String and a String to a float, as well as other constants and methods useful when dealing with a float.

Constant Summary

int	BYTES	The number of bytes used to represent a float value.
int	MAX_EXPONENT	Maximum exponent a finite float variable may have.
float	MAX_VALUE	A constant holding the largest positive finite value of type float, (2-2^-23)·2^127.
int	MIN_EXPONENT	Minimum exponent a normalized float variable may have.
float	MIN_NORMAL	A constant holding the smallest positive normal value of type float, 2^-126.
float	MIN_VALUE	A constant holding the smallest positive nonzero value of type float, 2^-149.
float	NEGATIVE_INFINITY	A constant holding the negative infinity of type float.
float	NaN	A constant holding a Not-a-Number (NaN) value of type float.
float	POSITIVE_INFINITY	A constant holding the positive infinity of type float.
int	SIZE	The number of bits used to represent a float value.

Field Summary

public static final Class<Float>

TYPE

The Class instance representing the primitive type float.

Public Constructor Summary

	Float(float value) Constructs a newly allocated Float object that represents the primitive float argument.
	Float(double value) Constructs a newly allocated Float object that represents the argument converted to type float.
	Float(String s) Constructs a newly allocated Float object that represents the floating-point value of type float represented by the string.

Public Method Summary

byte	byteValue() Returns the value of this Float as a byte after a narrowing primitive conversion.
static int	compare(float f1, float f2) Compares the two specified float values.
int	compareTo(Float anotherFloat) Compares two Float objects numerically.
double	doubleValue() Returns the value of this Float as a double after a widening primitive conversion.
boolean	equals(Object obj) Compares this object against the specified object.
static int	floatToIntBits(float value) Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout.
static int	floatToRawIntBits(float value) Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout, preserving Not-a-Number (NaN) values.
float	floatValue() Returns the float value of this Float object.
int	hashCode() Returns a hash code for this Float object.
static int	hashCode(float value) Returns a hash code for a float value; compatible with Float.hashCode().
static float	intBitsToFloat(int bits) Returns the float value corresponding to a given bit representation.
int	intValue() Returns the value of this Float as an int after a narrowing primitive conversion.
static boolean	isFinite(float f) Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
boolean	isInfinite() Returns true if this Float value is infinitely large in magnitude, false otherwise.
static boolean	isInfinite(float v) Returns true if the specified number is infinitely large in magnitude, false otherwise.
static boolean	isNaN(float v) Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
boolean	isNaN() Returns true if this Float value is a Not-a-Number (NaN), false otherwise.
long	longValue() Returns value of this Float as a long after a narrowing primitive conversion.
static float	max(float a, float b) Returns the greater of two float values as if by calling Math.max.
static float	min(float a, float b) Returns the smaller of two float values as if by calling Math.min.
static float	parseFloat(String s) Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.
short	shortValue() Returns the value of this Float as a short after a narrowing primitive conversion.
static float	sum(float a, float b) Adds two float values together as per the + operator.
static String	toHexString(float f) Returns a hexadecimal string representation of the float argument.
String	toString() Returns a string representation of this Float object.
static String	toString(float f) Returns a string representation of the float argument.
static Float	valueOf(String s) Returns a Float object holding the float value represented by the argument string s.
static Float	valueOf(float f) Returns a Float instance representing the specified float value.

Inherited Method Summary

From class java.lang.Number

byte	byteValue() Returns the value of the specified number as a byte, which may involve rounding or truncation.
abstract double	doubleValue() Returns the value of the specified number as a double, which may involve rounding.
abstract float	floatValue() Returns the value of the specified number as a float, which may involve rounding.
abstract int	intValue() Returns the value of the specified number as an int, which may involve rounding or truncation.
abstract long	longValue() Returns the value of the specified number as a long, which may involve rounding or truncation.
short	shortValue() Returns the value of the specified number as a short, which may involve rounding or truncation.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.lang.Comparable

abstract int

compareTo(Float o) Compares this object with the specified object for order.

Constants

public static final int BYTES

The number of bytes used to represent a float value.

Constant Value: 4

public static final int MAX_EXPONENT

Maximum exponent a finite float variable may have. It is equal to the value returned by Math.getExponent(Float.MAX_VALUE).

Constant Value: 127

public static final float MAX_VALUE

A constant holding the largest positive finite value of type float, (2-2^-23)·2¹²⁷. It is equal to the hexadecimal floating-point literal 0x1.fffffeP+127f and also equal to Float.intBitsToFloat(0x7f7fffff).

Constant Value: 3.4028235E38

public static final int MIN_EXPONENT

Minimum exponent a normalized float variable may have. It is equal to the value returned by Math.getExponent(Float.MIN_NORMAL).

Constant Value: -126

public static final float MIN_NORMAL

A constant holding the smallest positive normal value of type float, 2^-126. It is equal to the hexadecimal floating-point literal 0x1.0p-126f and also equal to Float.intBitsToFloat(0x00800000).

Constant Value: 1.17549435E-38

public static final float MIN_VALUE

A constant holding the smallest positive nonzero value of type float, 2^-149. It is equal to the hexadecimal floating-point literal 0x0.000002P-126f and also equal to Float.intBitsToFloat(0x1).

Constant Value: 1.4E-45

public static final float NEGATIVE_INFINITY

A constant holding the negative infinity of type float. It is equal to the value returned by Float.intBitsToFloat(0xff800000).

Constant Value: -Infinity

public static final float NaN

A constant holding a Not-a-Number (NaN) value of type float. It is equivalent to the value returned by Float.intBitsToFloat(0x7fc00000).

Constant Value: NaN

public static final float POSITIVE_INFINITY

A constant holding the positive infinity of type float. It is equal to the value returned by Float.intBitsToFloat(0x7f800000).

Constant Value: Infinity

public static final int SIZE

The number of bits used to represent a float value.

Constant Value: 32

Fields

public static final Class<Float> TYPE

The Class instance representing the primitive type float.

Public Constructors

public Float (float value)

Constructs a newly allocated Float object that represents the primitive float argument.

Parameters

value	the value to be represented by the Float.

public Float (double value)

Constructs a newly allocated Float object that represents the argument converted to type float.

Parameters

value	the value to be represented by the Float.

public Float (String s)

Constructs a newly allocated Float object that represents the floating-point value of type float represented by the string. The string is converted to a float value as if by the valueOf method.

Parameters

s	a string to be converted to a Float.

Throws

NumberFormatException	if the string does not contain a parsable number.

See Also

• valueOf(java.lang.String)

Public Methods

public byte byteValue ()

Returns the value of this Float as a byte after a narrowing primitive conversion.

Returns

• the float value represented by this object converted to type byte

public static int compare (float f1, float f2)

Compares the two specified float values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:

    new Float(f1).compareTo(new Float(f2))
 

Parameters

f1	the first float to compare.
f2	the second float to compare.

Returns

• the value 0 if f1 is numerically equal to f2; a value less than 0 if f1 is numerically less than f2; and a value greater than 0 if f1 is numerically greater than f2.

public int compareTo (Float anotherFloat)

Compares two Float objects numerically. There are two ways in which comparisons performed by this method differ from those performed by the Java language numerical comparison operators (<, <=, ==, >=, >) when applied to primitive float values:

• Float.NaN is considered by this method to be equal to itself and greater than all other float values (including Float.POSITIVE_INFINITY).
• 0.0f is considered by this method to be greater than -0.0f.

This ensures that the natural ordering of Float objects imposed by this method is consistent with equals.

Parameters

anotherFloat	the Float to be compared.

Returns

• the value 0 if anotherFloat is numerically equal to this Float; a value less than 0 if this Float is numerically less than anotherFloat; and a value greater than 0 if this Float is numerically greater than anotherFloat.

See Also

• Comparable.compareTo(Object)

public double doubleValue ()

Returns the value of this Float as a double after a widening primitive conversion.

Returns

• the float value represented by this object converted to type double

public boolean equals (Object obj)

Compares this object against the specified object. The result is true if and only if the argument is not null and is a Float object that represents a float with the same value as the float represented by this object. For this purpose, two float values are considered to be the same if and only if the method floatToIntBits(float) returns the identical int value when applied to each.

Note that in most cases, for two instances of class Float, f1 and f2, the value of f1.equals(f2) is true if and only if

   f1.floatValue() == f2.floatValue()
 

also has the value true. However, there are two exceptions:

• If f1 and f2 both represent Float.NaN, then the equals method returns true, even though Float.NaN==Float.NaN has the value false.
• If f1 represents +0.0f while f2 represents -0.0f, or vice versa, the equal test has the value false, even though 0.0f==-0.0f has the value true.

This definition allows hash tables to operate properly.

Parameters

obj	the object to be compared

Returns

• true if the objects are the same; false otherwise.

See Also

• floatToIntBits(float)

public static int floatToIntBits (float value)

Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout.

Bit 31 (the bit that is selected by the mask 0x80000000) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff) represent the significand (sometimes called the mantissa) of the floating-point number.

If the argument is positive infinity, the result is 0x7f800000.

If the argument is negative infinity, the result is 0xff800000.

If the argument is NaN, the result is 0x7fc00000.

In all cases, the result is an integer that, when given to the intBitsToFloat(int) method, will produce a floating-point value the same as the argument to floatToIntBits (except all NaN values are collapsed to a single "canonical" NaN value).

Parameters

value	a floating-point number.

Returns

• the bits that represent the floating-point number.

public static int floatToRawIntBits (float value)

Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout, preserving Not-a-Number (NaN) values.

Bit 31 (the bit that is selected by the mask 0x80000000) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff) represent the significand (sometimes called the mantissa) of the floating-point number.

If the argument is positive infinity, the result is 0x7f800000.

If the argument is negative infinity, the result is 0xff800000.

If the argument is NaN, the result is the integer representing the actual NaN value. Unlike the floatToIntBits method, floatToRawIntBits does not collapse all the bit patterns encoding a NaN to a single "canonical" NaN value.

In all cases, the result is an integer that, when given to the intBitsToFloat(int) method, will produce a floating-point value the same as the argument to floatToRawIntBits.

Parameters

value	a floating-point number.

Returns

• the bits that represent the floating-point number.

public float floatValue ()

Returns the float value of this Float object.

Returns

• the float value represented by this object

public int hashCode ()

Returns a hash code for this Float object. The result is the integer bit representation, exactly as produced by the method floatToIntBits(float), of the primitive float value represented by this Float object.

Returns

• a hash code value for this object.

public static int hashCode (float value)

Returns a hash code for a float value; compatible with Float.hashCode().

Parameters

value	the value to hash

Returns

• a hash code value for a float value.

public static float intBitsToFloat (int bits)

Returns the float value corresponding to a given bit representation. The argument is considered to be a representation of a floating-point value according to the IEEE 754 floating-point "single format" bit layout.

If the argument is 0x7f800000, the result is positive infinity.

If the argument is 0xff800000, the result is negative infinity.

If the argument is any value in the range 0x7f800001 through 0x7fffffff or in the range 0xff800001 through 0xffffffff, the result is a NaN. No IEEE 754 floating-point operation provided by Java can distinguish between two NaN values of the same type with different bit patterns. Distinct values of NaN are only distinguishable by use of the Float.floatToRawIntBits method.

In all other cases, let s, e, and m be three values that can be computed from the argument:

int s = ((bits >> 31) == 0) ? 1 : -1;
 int e = ((bits >> 23) & 0xff);
 int m = (e == 0) ?
                 (bits & 0x7fffff) << 1 :
                 (bits & 0x7fffff) | 0x800000;
 

Then the floating-point result equals the value of the mathematical expression s·m·2^e-150.

Note that this method may not be able to return a float NaN with exactly same bit pattern as the int argument. IEEE 754 distinguishes between two kinds of NaNs, quiet NaNs and signaling NaNs. The differences between the two kinds of NaN are generally not visible in Java. Arithmetic operations on signaling NaNs turn them into quiet NaNs with a different, but often similar, bit pattern. However, on some processors merely copying a signaling NaN also performs that conversion. In particular, copying a signaling NaN to return it to the calling method may perform this conversion. So intBitsToFloat may not be able to return a float with a signaling NaN bit pattern. Consequently, for some int values, floatToRawIntBits(intBitsToFloat(start)) may not equal start. Moreover, which particular bit patterns represent signaling NaNs is platform dependent; although all NaN bit patterns, quiet or signaling, must be in the NaN range identified above.

Parameters

bits	an integer.

Returns

• the float floating-point value with the same bit pattern.

public int intValue ()

Returns the value of this Float as an int after a narrowing primitive conversion.

Returns

• the float value represented by this object converted to type int

public static boolean isFinite (float f)

Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).

Parameters

f	the float value to be tested

Returns

• true if the argument is a finite floating-point value, false otherwise.

public boolean isInfinite ()

Returns true if this Float value is infinitely large in magnitude, false otherwise.

Returns

• true if the value represented by this object is positive infinity or negative infinity; false otherwise.

public static boolean isInfinite (float v)

Returns true if the specified number is infinitely large in magnitude, false otherwise.

Parameters

v	the value to be tested.

Returns

• true if the argument is positive infinity or negative infinity; false otherwise.

public static boolean isNaN (float v)

Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.

Parameters

v	the value to be tested.

Returns

• true if the argument is NaN; false otherwise.

public boolean isNaN ()

Returns true if this Float value is a Not-a-Number (NaN), false otherwise.

Returns

• true if the value represented by this object is NaN; false otherwise.

public long longValue ()

Returns value of this Float as a long after a narrowing primitive conversion.

Returns

• the float value represented by this object converted to type long

public static float max (float a, float b)

Returns the greater of two float values as if by calling Math.max.

Parameters

a	the first operand
b	the second operand

Returns

• the greater of a and b

See Also

• BinaryOperator

public static float min (float a, float b)

Returns the smaller of two float values as if by calling Math.min.

Parameters

a	the first operand
b	the second operand

Returns

• the smaller of a and b

See Also

• BinaryOperator

public static float parseFloat (String s)

Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.

Parameters

s	the string to be parsed.

Returns

• the float value represented by the string argument.

Throws

NullPointerException	if the string is null
NumberFormatException	if the string does not contain a parsable float.

See Also

• valueOf(String)

public short shortValue ()

Returns the value of this Float as a short after a narrowing primitive conversion.

Returns

• the float value represented by this object converted to type short

public static float sum (float a, float b)

Adds two float values together as per the + operator.

Parameters

a	the first operand
b	the second operand

Returns

• the sum of a and b

See Also

• BinaryOperator

public static String toHexString (float f)

Returns a hexadecimal string representation of the float argument. All characters mentioned below are ASCII characters.

• If the argument is NaN, the result is the string "NaN".
• Otherwise, the result is a string that represents the sign and magnitude (absolute value) of the argument. If the sign is negative, the first character of the result is '-' ('\u002D'); if the sign is positive, no sign character appears in the result. As for the magnitude m:
  • If m is infinity, it is represented by the string "Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity".
  • If m is zero, it is represented by the string "0x0.0p0"; thus, negative zero produces the result "-0x0.0p0" and positive zero produces the result "0x0.0p0".
  • If m is a float value with a normalized representation, substrings are used to represent the significand and exponent fields. The significand is represented by the characters "0x1." followed by a lowercase hexadecimal representation of the rest of the significand as a fraction. Trailing zeros in the hexadecimal representation are removed unless all the digits are zero, in which case a single zero is used. Next, the exponent is represented by "p" followed by a decimal string of the unbiased exponent as if produced by a call to Integer.toString on the exponent value.
  • If m is a float value with a subnormal representation, the significand is represented by the characters "0x0." followed by a hexadecimal representation of the rest of the significand as a fraction. Trailing zeros in the hexadecimal representation are removed. Next, the exponent is represented by "p-126". Note that there must be at least one nonzero digit in a subnormal significand.

Examples

Floating-point Value	Hexadecimal String
1.0	0x1.0p0
-1.0	-0x1.0p0
2.0	0x1.0p1
3.0	0x1.8p1
0.5	0x1.0p-1
0.25	0x1.0p-2
Float.MAX_VALUE	0x1.fffffep127
Minimum Normal Value	0x1.0p-126
Maximum Subnormal Value	0x0.fffffep-126
Float.MIN_VALUE	0x0.000002p-126

Parameters

f	the float to be converted.

Returns

• a hex string representation of the argument.

public String toString ()

Returns a string representation of this Float object. The primitive float value represented by this object is converted to a String exactly as if by the method toString of one argument.

Returns

• a String representation of this object.

See Also

• toString(float)

public static String toString (float f)

Returns a string representation of the float argument. All characters mentioned below are ASCII characters.

• If the argument is NaN, the result is the string "NaN".
• Otherwise, the result is a string that represents the sign and magnitude (absolute value) of the argument. If the sign is negative, the first character of the result is '-' ('\u002D'); if the sign is positive, no sign character appears in the result. As for the magnitude m:
  • If m is infinity, it is represented by the characters "Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity".
  • If m is zero, it is represented by the characters "0.0"; thus, negative zero produces the result "-0.0" and positive zero produces the result "0.0".
  • If m is greater than or equal to 10^-3 but less than 10⁷, then it is represented as the integer part of m, in decimal form with no leading zeroes, followed by '.' ('\u002E'), followed by one or more decimal digits representing the fractional part of m.
  • If m is less than 10^-3 or greater than or equal to 10⁷, then it is represented in so-called "computerized scientific notation." Let n be the unique integer such that 10ⁿ ≤ m < 10ⁿ⁺¹; then let a be the mathematically exact quotient of m and 10ⁿ so that 1 ≤ a < 10. The magnitude is then represented as the integer part of a, as a single decimal digit, followed by '.' ('\u002E'), followed by decimal digits representing the fractional part of a, followed by the letter 'E' ('\u0045'), followed by a representation of n as a decimal integer, as produced by the method Integer.toString(int).

How many digits must be printed for the fractional part of m or a? There must be at least one digit to represent the fractional part, and beyond that as many, but only as many, more digits as are needed to uniquely distinguish the argument value from adjacent values of type float. That is, suppose that x is the exact mathematical value represented by the decimal representation produced by this method for a finite nonzero argument f. Then f must be the float value nearest to x; or, if two float values are equally close to x, then f must be one of them and the least significant bit of the significand of f must be 0.

To create localized string representations of a floating-point value, use subclasses of NumberFormat.

Parameters

f	the float to be converted.

Returns

• a string representation of the argument.

public static Float valueOf (String s)

Returns a Float object holding the float value represented by the argument string s.

If s is null, then a NullPointerException is thrown.

Leading and trailing whitespace characters in s are ignored. Whitespace is removed as if by the String.trim() method; that is, both ASCII space and control characters are removed. The rest of s should constitute a FloatValue as described by the lexical syntax rules:

FloatValue:

Sign_opt NaN

Sign_opt Infinity

Sign_opt FloatingPointLiteral

Sign_opt HexFloatingPointLiteral

SignedInteger

HexFloatingPointLiteral:

HexSignificand BinaryExponent FloatTypeSuffix_opt

HexSignificand:

HexNumeral

HexNumeral .

0x HexDigits_opt . HexDigits

0X HexDigits_opt . HexDigits

BinaryExponent:

BinaryExponentIndicator SignedInteger

BinaryExponentIndicator:

p

P

where Sign, FloatingPointLiteral, HexNumeral, HexDigits, SignedInteger and FloatTypeSuffix are as defined in the lexical structure sections of The Java™ Language Specification, except that underscores are not accepted between digits. If s does not have the form of a FloatValue, then a NumberFormatException is thrown. Otherwise, s is regarded as representing an exact decimal value in the usual "computerized scientific notation" or as an exact hexadecimal value; this exact numerical value is then conceptually converted to an "infinitely precise" binary value that is then rounded to type float by the usual round-to-nearest rule of IEEE 754 floating-point arithmetic, which includes preserving the sign of a zero value. Note that the round-to-nearest rule also implies overflow and underflow behaviour; if the exact value of s is large enough in magnitude (greater than or equal to (MAX_VALUE + ulp(MAX_VALUE)/2), rounding to float will result in an infinity and if the exact value of s is small enough in magnitude (less than or equal to MIN_VALUE/2), rounding to float will result in a zero. Finally, after rounding a Float object representing this float value is returned.

To interpret localized string representations of a floating-point value, use subclasses of NumberFormat.

Note that trailing format specifiers, specifiers that determine the type of a floating-point literal (1.0f is a float value; 1.0d is a double value), do not influence the results of this method. In other words, the numerical value of the input string is converted directly to the target floating-point type. In general, the two-step sequence of conversions, string to double followed by double to float, is not equivalent to converting a string directly to float. For example, if first converted to an intermediate double and then to float, the string
"1.00000017881393421514957253748434595763683319091796875001d"
results in the float value 1.0000002f; if the string is converted directly to float, 1.0000001f results.

To avoid calling this method on an invalid string and having a NumberFormatException be thrown, the documentation for Double.valueOf lists a regular expression which can be used to screen the input.

Parameters

s	the string to be parsed.

Returns

• a Float object holding the value represented by the String argument.

Throws

NumberFormatException	if the string does not contain a parsable number.

public static Float valueOf (float f)

Returns a Float instance representing the specified float value. If a new Float instance is not required, this method should generally be used in preference to the constructor Float(float), as this method is likely to yield significantly better space and time performance by caching frequently requested values.

Parameters

f	a float value.

Returns

• a Float instance representing f.