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Float

public final class Float
extends Number implements Comparable<Float>

java.lang.Object
   ↳ java.lang.Number
     ↳ java.lang.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.

Summary

Constants

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)·2127.

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.

Fields

public static final Class<Float> TYPE

The Class instance representing the primitive type float.

Public constructors

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 methods

byte byteValue()

Returns the value of this Float as a byte (by casting to a byte).

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 double value of this Float object.

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 (by casting to type int).

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 (by casting to type long).

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 (by casting to a short).

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 methods

From class java.lang.Number
From class java.lang.Object
From interface java.lang.Comparable

Constants

BYTES

Added in API level 24
int BYTES

The number of bytes used to represent a float value.

Constant Value: 4 (0x00000004)

MAX_EXPONENT

Added in API level 9
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 (0x0000007f)

MAX_VALUE

Added in API level 1
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

MIN_EXPONENT

Added in API level 9
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 (0xffffff82)

MIN_NORMAL

Added in API level 9
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

MIN_VALUE

Added in API level 1
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

NEGATIVE_INFINITY

Added in API level 1
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

NaN

Added in API level 1
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

POSITIVE_INFINITY

Added in API level 1
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

SIZE

Added in API level 1
int SIZE

The number of bits used to represent a float value.

Constant Value: 32 (0x00000020)

Fields

TYPE

Added in API level 1
Class<Float> TYPE

The Class instance representing the primitive type float.

Public constructors

Float

Added in API level 1
Float (float value)

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

Parameters
value float: the value to be represented by the Float.

Float

Added in API level 1
Float (double value)

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

Parameters
value double: the value to be represented by the Float.

Float

Added in API level 1
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 String: a string to be converted to a Float.
Throws
NumberFormatException if the string does not contain a parsable number.

See also:

Public methods

byteValue

Added in API level 1
byte byteValue ()

Returns the value of this Float as a byte (by casting to a byte).

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

compare

Added in API level 1
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 float: the first float to compare.
f2 float: the second float to compare.
Returns
int 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.

compareTo

Added in API level 1
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 Float: the Float to be compared.
Returns
int 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:

doubleValue

Added in API level 1
double doubleValue ()

Returns the double value of this Float object.

Returns
double the float value represented by this object is converted to type double and the result of the conversion is returned.

equals

Added in API level 1
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 Object: the object to be compared
Returns
boolean true if the objects are the same; false otherwise.

See also:

floatToIntBits

Added in API level 1
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 float: a floating-point number.
Returns
int the bits that represent the floating-point number.

floatToRawIntBits

Added in API level 1
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 float: a floating-point number.
Returns
int the bits that represent the floating-point number.

floatValue

Added in API level 1
float floatValue ()

Returns the float value of this Float object.

Returns
float the float value represented by this object

hashCode

Added in API level 1
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
int a hash code value for this object.

hashCode

Added in API level 24
int hashCode (float value)

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

Parameters
value float: the value to hash
Returns
int a hash code value for a float value.

intBitsToFloat

Added in API level 1
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·2e-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 int: an integer.
Returns
float the float floating-point value with the same bit pattern.

intValue

Added in API level 1
int intValue ()

Returns the value of this Float as an int (by casting to type int).

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

isFinite

Added in API level 24
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 float: the float value to be tested
Returns
boolean true if the argument is a finite floating-point value, false otherwise.

isInfinite

Added in API level 1
boolean isInfinite ()

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

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

isInfinite

Added in API level 1
boolean isInfinite (float v)

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

Parameters
v float: the value to be tested.
Returns
boolean true if the argument is positive infinity or negative infinity; false otherwise.

isNaN

Added in API level 1
boolean isNaN (float v)

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

Parameters
v float: the value to be tested.
Returns
boolean true if the argument is NaN; false otherwise.

isNaN

Added in API level 1
boolean isNaN ()

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

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

longValue

Added in API level 1
long longValue ()

Returns value of this Float as a long (by casting to type long).

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

max

Added in API level 24
float max (float a, 
                float b)

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

Parameters
a float: the first operand
b float: the second operand
Returns
float the greater of a and b

See also:

min

Added in API level 24
float min (float a, 
                float b)

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

Parameters
a float: the first operand
b float: the second operand
Returns
float the smaller of a and b

See also:

parseFloat

Added in API level 1
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 String: the string to be parsed.
Returns
float 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:

shortValue

Added in API level 1
short shortValue ()

Returns the value of this Float as a short (by casting to a short).

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

sum

Added in API level 24
float sum (float a, 
                float b)

Adds two float values together as per the + operator.

Parameters
a float: the first operand
b float: the second operand
Returns
float the sum of a and b

See also:

toHexString

Added in API level 1
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 ValueHexadecimal 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 float: the float to be converted.
Returns
String a hex string representation of the argument.

toString

Added in API level 1
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
String a String representation of this object.

See also:

toString

Added in API level 1
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 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 float: the float to be converted.
Returns
String a string representation of the argument.

valueOf

Added in API level 1
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 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:
Signopt NaN
Signopt Infinity
Signopt FloatingPointLiteral
Signopt HexFloatingPointLiteral
SignedInteger

HexFloatingPointLiteral:
HexSignificand BinaryExponent FloatTypeSuffixopt

HexSignificand:
HexNumeral
HexNumeral .
0x HexDigitsopt . HexDigits
0X HexDigitsopt . 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 String: the string to be parsed.
Returns
Float a Float object holding the value represented by the String argument.
Throws
NumberFormatException if the string does not contain a parsable number.

valueOf

Added in API level 1
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 float: a float value.
Returns
Float a Float instance representing f.
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