java.lang
Class Float

java.lang.Object
  java.lang.Float

public final class Float
extends Object

Minimal Float implementation that supports floatToIntBits and intBitsToFloat

Author:

Lawrie Griffiths

Method Summary

static int	floatToIntBits(float value) Returns the bit represention of a single-float value.
static float	intBitsToFloat(int value) Returns the single-float corresponding to a given bit represention.
static float	parseFloat(String s) Converts a String value into a float
String	toString(float f)

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait

Method Detail

floatToIntBits

public static 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 (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. The lejos implementation behaves like floatToRawIntBits and does not collapse NaN values.

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

Parameters:

value - a floating-point number.

Returns:

the bits that represent the floating-point number.

intBitsToFloat

public static float intBitsToFloat(int value)

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 0x7fffffff or in the range 0xff800001 through 0xffffffff, the result is NaN. All IEEE 754 NaN values of type float are, in effect, lumped together by the Java programming language into a single float value called NaN. Distinct values of NaN are only accessible 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.

Parameters:

value - an integer.

Returns:

the single-format floating-point value with the same bit pattern.

parseFloat

public static float parseFloat(String s)
                        throws NumberFormatException

Converts a String value into a float

Parameters:

s - String representation of float. Must only contain numbers and an optional decimal, and optional - sign at front.

Returns:

float number

Throws:

NumberFormatException

toString

public String toString(float f)