Class java.lang.Float - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.lang.Float

java.lang.Object
   |
   +----java.lang.Number
           |
           +----java.lang.Float

public final class Float
extends Number

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.

MAX_VALUE: The largest positive value of type float.
MIN_VALUE: The smallest positive value of type float.
NaN: The NaN value of type float.
NEGATIVE_INFINITY: The negative infinity of type float.
POSITIVE_INFINITY: The positive infinity of type float.
TYPE: The Class object representing the primitive type float.

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

byteValue(): Returns the value of this Float as a byte (by casting to a byte).
doubleValue(): Returns the double value of this Float.
equals(Object): Compares this object against some other object.
floatToIntBits(float): Returns the bit represention of a single-float value.
floatValue(): Returns the float value of this Float object.
hashCode(): Returns a hashcode for this Float.
intBitsToFloat(int): Returns the single-float corresponding to a given bit represention.
intValue(): Returns the integer value of this Float (by casting to an int).
isInfinite(): Returns true if this Float value is infinitely large in magnitude.
isInfinite(float): Returns true if the specified number is infinitely large in magnitude.
isNaN(): Returns true if this Float value is Not-a-Number (NaN).
isNaN(float): Returns true if the specified number is the special Not-a-Number (NaN) value.
longValue(): Returns the long value of this Float (by casting to a long).
shortValue(): Returns the value of this Float as a short (by casting to a short).
toString(): Returns a String representation of this Float object.
toString(float): Returns a String representation for the specified float value.
valueOf(String): Returns the floating point value represented by the specified String.

POSITIVE_INFINITY

 public static final float POSITIVE_INFINITY

The positive infinity of type float.

NEGATIVE_INFINITY

 public static final float NEGATIVE_INFINITY

The negative infinity of type float.

NaN

 public static final float NaN

The NaN value of type float.

MAX_VALUE

 public static final float MAX_VALUE

The largest positive value of type float.

MIN_VALUE

 public static final float MIN_VALUE

The smallest positive value of type float.

TYPE

 public static final Class TYPE

The Class object representing the primitive type float.

Float

 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.

Float

 public Float(double value)

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

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

Float

 public Float(String s) throws NumberFormatException

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

toString

 public static String toString(float f)

Returns a String representation for the specified float value.

The values NaN, NEGATIVE_INFINITY, POSITIVE_INFINITY, -0.0, and +0.0 are represented by the strings "NaN", "-Infinity", "Infinity", "-0.0", and "0.0", respectively.

If d is in the range 10^-3 <= |d| <= 10⁷, then it is converted to a String in the style [-]ddd.ddd. Otherwise, it is converted to a string in the style [-]m.ddddE±xx.

There is always a minimum of 1 digit after the decimal point. The number of digits is the minimum needed to uniquely distinguish the argument value from adjacent values of type float.

Parameters:: d - the float to be converted.
Returns:: a string representation of the argument.

valueOf

 public static Float valueOf(String s) throws NumberFormatException

Returns the floating point value represented by the specified String.

Parameters:: s - the string to be parsed.
Returns:: a newly constructed Float initialized to the value represented by the String argument.
Throws: NumberFormatException: if the string does not contain a parsable number.

isNaN

 public static boolean isNaN(float v)

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

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

isInfinite

 public static boolean isInfinite(float v)

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

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

isNaN

 public boolean isNaN()

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

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

isInfinite

 public boolean isInfinite()

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

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

toString

 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.
Overrides:: toString in class Object
See Also:: toString

byteValue

 public byte byteValue()

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

Overrides:: byteValue in class Number

shortValue

 public short shortValue()

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

Overrides:: shortValue in class Number

intValue

 public int intValue()

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

Returns:: the float value represented by this object converted to type int and the result of the conversion is returned.
Overrides:: intValue in class Number

longValue

 public long longValue()

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

Returns:: the float value represented by this object is converted to type long and the result of the conversion is returned.
Overrides:: longValue in class Number

floatValue

 public float floatValue()

Returns the float value of this Float object.

Returns:: the float value represented by this object.
Overrides:: floatValue in class Number

doubleValue

 public double doubleValue()

Returns the double value of this Float.

Overrides:: doubleValue in class Number

hashCode

 public int hashCode()

Returns a hashcode for this Float.

Returns:: a hash code value for this object.
Overrides:: hashCode in class Object

equals

 public boolean equals(Object obj)

Compares this object against some other object. The result is true if and only if the argument is not null and is a Float object that represents a float that has the identical bit pattern to the bit pattern of the float represented by this object.

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.

Returns:: true if the objects are the same; false otherwise.
Overrides:: equals in class Object
See Also:: floatToIntBits

floatToIntBits

 public static native int floatToIntBits(float value)

Returns the bit represention of a single-float value. The result is a representation of the floating-point argument according to the IEEE 754 floating-point "single precision" bit layout.

Bit 31 represents the sign of the floating-point number. Bits 30-23 represent the exponent. Bits 22-0 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.

Parameters:: value - a floating-point number.
Returns:: the bits that represent the floating-point number.

intBitsToFloat

 public static native float intBitsToFloat(int bits)

Returns the single-float corresponding to a given bit represention. The argument is considered to be a representation of a floating-point value according to the IEEE 754 floating-point "single precision" 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 0x7f8fffff or in the range 0xff800001 through 0xff8fffff, the result is NaN. All IEEE 754 NaN values are, in effect, lumped together by the Java language into a single value.

Parameters:: bits - an integer.
Returns:: the single-format floating-point value with the same bit pattern.

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