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java.lang
public final class: Float [javadoc | source]
java.lang.Object
   java.lang.Number
      java.lang.Float

All Implemented Interfaces:
    Comparable, Serializable

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

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

Field Summary
public static final  float POSITIVE_INFINITY    A constant holding the positive infinity of type {@code float}. It is equal to the value returned by {@code Float.intBitsToFloat(0x7f800000)}. 
public static final  float NEGATIVE_INFINITY    A constant holding the negative infinity of type {@code float}. It is equal to the value returned by {@code Float.intBitsToFloat(0xff800000)}. 
public static final  float NaN    A constant holding a Not-a-Number (NaN) value of type {@code float}. It is equivalent to the value returned by {@code Float.intBitsToFloat(0x7fc00000)}. 
public static final  float MAX_VALUE    A constant holding the largest positive finite value of type {@code float}, (2-2-23)·2127. It is equal to the hexadecimal floating-point literal {@code 0x1.fffffeP+127f} and also equal to {@code Float.intBitsToFloat(0x7f7fffff)}. 
public static final  float MIN_NORMAL    A constant holding the smallest positive normal value of type {@code float}, 2-126. It is equal to the hexadecimal floating-point literal {@code 0x1.0p-126f} and also equal to {@code Float.intBitsToFloat(0x00800000)}.
    since: 1.6 -
 
public static final  float MIN_VALUE    A constant holding the smallest positive nonzero value of type {@code float}, 2-149. It is equal to the hexadecimal floating-point literal {@code 0x0.000002P-126f} and also equal to {@code Float.intBitsToFloat(0x1)}. 
public static final  int MAX_EXPONENT    Maximum exponent a finite {@code float} variable may have. It is equal to the value returned by {@code Math.getExponent(Float.MAX_VALUE)}.
    since: 1.6 -
 
public static final  int MIN_EXPONENT    Minimum exponent a normalized {@code float} variable may have. It is equal to the value returned by {@code Math.getExponent(Float.MIN_NORMAL)}.
    since: 1.6 -
 
public static final  int SIZE    The number of bits used to represent a {@code float} value.
    since: 1.5 -
 
public static final  Class<Float> TYPE    The {@code Class} instance representing the primitive type {@code float}.
    since: JDK1.1 -
 
Constructor:
 public Float(float value) 
 public Float(double value) 
 public Float(String s) throws NumberFormatException 
    Constructs a newly allocated {@code Float} object that represents the floating-point value of type {@code float} represented by the string. The string is converted to a {@code float} value as if by the {@code valueOf} method.
    Parameters:
    s - a string to be converted to a {@code Float}.
    Throws:
    NumberFormatException - if the string does not contain a parsable number.
    Also see:
    java.lang.Float#valueOf(java.lang.String)
Method from java.lang.Float Summary:
byteValue,   compare,   compareTo,   doubleValue,   equals,   floatToIntBits,   floatToRawIntBits,   floatValue,   hashCode,   intBitsToFloat,   intValue,   isInfinite,   isInfinite,   isNaN,   isNaN,   longValue,   parseFloat,   shortValue,   toHexString,   toString,   toString,   valueOf,   valueOf
Methods from java.lang.Number:
byteValue,   doubleValue,   floatValue,   intValue,   longValue,   shortValue
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from java.lang.Float Detail:
 public byte byteValue() 
    Returns the value of this {@code Float} as a {@code byte} (by casting to a {@code byte}).
 public static int compare(float f1,
    float f2) 
    Compares the two specified {@code 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))
    
 public int compareTo(Float anotherFloat) 
    Compares two {@code 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 ({@code <, <=, ==, >=, >}) when applied to primitive {@code float} values:
    • {@code Float.NaN} is considered by this method to be equal to itself and greater than all other {@code float} values (including {@code Float.POSITIVE_INFINITY}).
    • {@code 0.0f} is considered by this method to be greater than {@code -0.0f}.
    This ensures that the natural ordering of {@code Float} objects imposed by this method is consistent with equals.
 public double doubleValue() 
    Returns the {@code double} value of this {@code Float} object.
 public boolean equals(Object obj) 
    Compares this object against the specified object. The result is {@code true} if and only if the argument is not {@code null} and is a {@code Float} object that represents a {@code float} with the same value as the {@code float} represented by this object. For this purpose, two {@code float} values are considered to be the same if and only if the method #floatToIntBits(float) returns the identical {@code int} value when applied to each.

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

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

    also has the value {@code true}. However, there are two exceptions:

    • If {@code f1} and {@code f2} both represent {@code Float.NaN}, then the {@code equals} method returns {@code true}, even though {@code Float.NaN==Float.NaN} has the value {@code false}.
    • If {@code f1} represents {@code +0.0f} while {@code f2} represents {@code -0.0f}, or vice versa, the {@code equal} test has the value {@code false}, even though {@code 0.0f==-0.0f} has the value {@code true}.
    This definition allows hash tables to operate properly.
 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 {@code 0x80000000}) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask {@code 0x7f800000}) represent the exponent. Bits 22-0 (the bits that are selected by the mask {@code 0x007fffff}) represent the significand (sometimes called the mantissa) of the floating-point number.

    If the argument is positive infinity, the result is {@code 0x7f800000}.

    If the argument is negative infinity, the result is {@code 0xff800000}.

    If the argument is NaN, the result is {@code 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 {@code floatToIntBits} (except all NaN values are collapsed to a single "canonical" NaN value).

 public static native 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 {@code 0x80000000}) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask {@code 0x7f800000}) represent the exponent. Bits 22-0 (the bits that are selected by the mask {@code 0x007fffff}) represent the significand (sometimes called the mantissa) of the floating-point number.

    If the argument is positive infinity, the result is {@code 0x7f800000}.

    If the argument is negative infinity, the result is {@code 0xff800000}.

    If the argument is NaN, the result is the integer representing the actual NaN value. Unlike the {@code floatToIntBits} method, {@code 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 {@code floatToRawIntBits}.

 public float floatValue() 
    Returns the {@code float} value of this {@code Float} object.
 public int hashCode() 
    Returns a hash code for this {@code Float} object. The result is the integer bit representation, exactly as produced by the method #floatToIntBits(float) , of the primitive {@code float} value represented by this {@code Float} object.
 public static native float intBitsToFloat(int bits)
    Returns the {@code 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 {@code 0x7f800000}, the result is positive infinity.

    If the argument is {@code 0xff800000}, the result is negative infinity.

    If the argument is any value in the range {@code 0x7f800001} through {@code 0x7fffffff} or in the range {@code 0xff800001} through {@code 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 {@code 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 {@code float} NaN with exactly same bit pattern as the {@code 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 {@code intBitsToFloat} may not be able to return a {@code float} with a signaling NaN bit pattern. Consequently, for some {@code int} values, {@code floatToRawIntBits(intBitsToFloat(start))} may not equal {@code 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.

 public int intValue() 
    Returns the value of this {@code Float} as an {@code int} (by casting to type {@code int}).
 public boolean isInfinite() 
    Returns {@code true} if this {@code Float} value is infinitely large in magnitude, {@code false} otherwise.
 public static boolean isInfinite(float v) 
    Returns {@code true} if the specified number is infinitely large in magnitude, {@code false} otherwise.
 public boolean isNaN() 
    Returns {@code true} if this {@code Float} value is a Not-a-Number (NaN), {@code false} otherwise.
 public static boolean isNaN(float v) 
    Returns {@code true} if the specified number is a Not-a-Number (NaN) value, {@code false} otherwise.
 public long longValue() 
    Returns value of this {@code Float} as a {@code long} (by casting to type {@code long}).
 public static float parseFloat(String s) throws NumberFormatException 
    Returns a new {@code float} initialized to the value represented by the specified {@code String}, as performed by the {@code valueOf} method of class {@code Float}.
 public short shortValue() 
    Returns the value of this {@code Float} as a {@code short} (by casting to a {@code short}).
 public static String toHexString(float f) 
    Returns a hexadecimal string representation of the {@code float} argument. All characters mentioned below are ASCII characters.
    • If the argument is NaN, the result is the string "{@code 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 '{@code -}' ('\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 {@code "Infinity"}; thus, positive infinity produces the result {@code "Infinity"} and negative infinity produces the result {@code "-Infinity"}.
      • If m is zero, it is represented by the string {@code "0x0.0p0"}; thus, negative zero produces the result {@code "-0x0.0p0"} and positive zero produces the result {@code "0x0.0p0"}.
      • If m is a {@code float} value with a normalized representation, substrings are used to represent the significand and exponent fields. The significand is represented by the characters {@code "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 {@code "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 {@code float} value with a subnormal representation, the significand is represented by the characters {@code "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 {@code "p-126"}. Note that there must be at least one nonzero digit in a subnormal significand.

    Examples

    Floating-point ValueHexadecimal String
    {@code 1.0} {@code 0x1.0p0}
    {@code -1.0} {@code -0x1.0p0}
    {@code 2.0} {@code 0x1.0p1}
    {@code 3.0} {@code 0x1.8p1}
    {@code 0.5} {@code 0x1.0p-1}
    {@code 0.25} {@code 0x1.0p-2}
    {@code Float.MAX_VALUE} {@code 0x1.fffffep127}
    {@code Minimum Normal Value} {@code 0x1.0p-126}
    {@code Maximum Subnormal Value} {@code 0x0.fffffep-126}
    {@code Float.MIN_VALUE} {@code 0x0.000002p-126}
 public String toString() 
    Returns a string representation of this {@code Float} object. The primitive {@code float} value represented by this object is converted to a {@code String} exactly as if by the method {@code toString} of one argument.
 public static String toString(float f) 
    Returns a string representation of the {@code float} argument. All characters mentioned below are ASCII characters.
    • If the argument is NaN, the result is the string "{@code 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 '{@code -}' ('\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 {@code "Infinity"}; thus, positive infinity produces the result {@code "Infinity"} and negative infinity produces the result {@code "-Infinity"}.
      • If m is zero, it is represented by the characters {@code "0.0"}; thus, negative zero produces the result {@code "-0.0"} and positive zero produces the result {@code "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 '{@code .}' ('\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 {@literal <} 10n+1; then let a be the mathematically exact quotient of m and 10n so that 1 ≤ a {@literal <} 10. The magnitude is then represented as the integer part of a, as a single decimal digit, followed by '{@code .}' ('\u002E'), followed by decimal digits representing the fractional part of a, followed by the letter '{@code E}' ('\u0045'), followed by a representation of n as a decimal integer, as produced by the method java.lang.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 {@code 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 {@code float} value nearest to x; or, if two {@code 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 {@code 0}.

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

 public static Float valueOf(String s) throws NumberFormatException 
    Returns a {@code Float} object holding the {@code float} value represented by the argument string {@code s}.

    If {@code s} is {@code null}, then a {@code NullPointerException} is thrown.

    Leading and trailing whitespace characters in {@code 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 {@code s} should constitute a FloatValue as described by the lexical syntax rules:

    FloatValue:
    Signopt {@code NaN}
    Signopt {@code Infinity}
    Signopt FloatingPointLiteral
    Signopt HexFloatingPointLiteral
    SignedInteger

    HexFloatingPointLiteral:
    HexSignificand BinaryExponent FloatTypeSuffixopt

    HexSignificand:
    HexNumeral
    HexNumeral {@code .}
    {@code 0x} HexDigitsopt {@code .} HexDigits
    {@code 0X} HexDigitsopt {@code .} HexDigits

    BinaryExponent:
    BinaryExponentIndicator SignedInteger

    BinaryExponentIndicator:
    {@code p}
    {@code 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 {@code s} does not have the form of a FloatValue, then a {@code NumberFormatException} is thrown. Otherwise, {@code 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 {@code 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 {@code s} is large enough in magnitude (greater than or equal to (#MAX_VALUE + ulp(MAX_VALUE) /2), rounding to {@code float} will result in an infinity and if the exact value of {@code 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 {@code Float} object representing this {@code float} value is returned.

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

    Note that trailing format specifiers, specifiers that determine the type of a floating-point literal ({@code 1.0f} is a {@code float} value; {@code 1.0d} is a {@code 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 {@code double} followed by {@code double} to {@code float}, is not equivalent to converting a string directly to {@code float}. For example, if first converted to an intermediate {@code double} and then to {@code float}, the string
    {@code "1.00000017881393421514957253748434595763683319091796875001d"}
    results in the {@code float} value {@code 1.0000002f}; if the string is converted directly to {@code float}, 1.0000001f results.

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

 public static Float valueOf(float f) 
    Returns a {@code Float} instance representing the specified {@code float} value. If a new {@code 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.