Float represent primitive
* float values.
*
* Additionally, this class provides various helper functions and variables
* related to floats.
*
* @author Paul Fisher
* @author Andrew Haley double may represent
* is 3.4028235e+38f.
*/
public static final float MAX_VALUE = 3.4028235e+38f;
/**
* The minimum positive value a float may represent
* is 1.4e-45.
*/
public static final float MIN_VALUE = 1.4e-45f;
/**
* The value of a float representation -1.0/0.0, negative infinity.
*/
public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
/**
* The value of a float representation 1.0/0.0, positive infinity.
*/
public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
/**
* All IEEE 754 values of NaN have the same value in Java.
*/
public static final float NaN = 0.0f / 0.0f;
/**
* The primitive type float is represented by this
* Class object.
* @since 1.1
*/
public static final Class TYPE = VMClassLoader.getPrimitiveClass('F');
/**
* The immutable value of this Float.
*
* @serial the wrapped float
*/
private final float value;
/**
* Create a Float from the primitive float
* specified.
*
* @param value the float argument
*/
public Float(float value)
{
this.value = value;
}
/**
* Create a Float from the primitive double
* specified.
*
* @param value the double argument
*/
public Float(double value)
{
this.value = (float) value;
}
/**
* Create a Float from the specified String.
* This method calls Float.parseFloat().
*
* @param s the String to convert
* @throws NumberFormatException if s cannot be parsed as a
* float
* @throws NullPointerException if s is null
* @see #parseFloat(String)
*/
public Float(String s)
{
value = parseFloat(s);
}
/**
* Convert the float to a String.
* Floating-point string representation is fairly complex: here is a
* rundown of the possible values. "[-]" indicates that a
* negative sign will be printed if the value (or exponent) is negative.
* "<number>" means a string of digits ('0' to '9').
* "<digit>" means a single digit ('0' to '9').| Value of Float | String Representation |
|---|---|
| [+-] 0 | [-]0.0 |
| Between [+-] 10-3 and 107, exclusive | *[-]number.number |
| Other numeric value | *[-]<digit>.<number>
* E[-]<number> |
| [+-] infinity | [-]Infinity |
| NaN | NaN |
. and at least one digit printed after
* it: even if the number is 3, it will be printed as 3.0.
* After the ".", all digits will be printed except trailing zeros. The
* result is rounded to the shortest decimal number which will parse back
* to the same float.
*
* To create other output formats, use {@link java.text.NumberFormat}.
*
* @XXX specify where we are not in accord with the spec.
*
* @param f the float to convert
* @return the String representing the float
*/
public static String toString(float f)
{
return Double.toString(f, true);
}
/**
* Creates a new Float object using the String.
*
* @param s the String to convert
* @return the new Float
* @throws NumberFormatException if s cannot be parsed as a
* float
* @throws NullPointerException if s is null
* @see #parseFloat(String)
*/
public static Float valueOf(String s)
{
return new Float(parseFloat(s));
}
/**
* Parse the specified String as a float. The
* extended BNF grammar is as follows:
*
* DecodableString: * ( [* *-|+]NaN) * | ( [-|+]Infinity) * | ( [-|+] FloatingPoint * [f|F|d* |D] ) * FloatingPoint: * ( { Digit }+ [.{ Digit } ] * [ Exponent ] ) * | (.{ Digit }+ [ Exponent ] ) * Exponent: * ( (e|E) * [-|+] { Digit }+ ) * Digit:'0'through'9'*
NaN and infinity are special cases, to allow parsing of the output * of toString. Otherwise, the result is determined by calculating * n * 10exponent to infinite precision, then rounding * to the nearest float. Remember that many numbers cannot be precisely * represented in floating point. In case of overflow, infinity is used, * and in case of underflow, signed zero is used. Unlike Integer.parseInt, * this does not accept Unicode digits outside the ASCII range. * *
If an unexpected character is found in the String, a
* NumberFormatException will be thrown. Leading and trailing
* 'whitespace' is ignored via String.trim(), but spaces
* internal to the actual number are not allowed.
*
*
To parse numbers according to another format, consider using
* {@link java.text.NumberFormat}.
*
* @XXX specify where/how we are not in accord with the spec.
*
* @param str the String to convert
* @return the float value of s
* @throws NumberFormatException if s cannot be parsed as a
* float
* @throws NullPointerException if s is null
* @see #MIN_VALUE
* @see #MAX_VALUE
* @see #POSITIVE_INFINITY
* @see #NEGATIVE_INFINITY
* @since 1.2
*/
public static float parseFloat(String s)
{
// XXX Rounding parseDouble() causes some errors greater than 1 ulp from
// the infinitely precise decimal.
return (float) Double.parseDouble(s);
}
/**
* Return true if the float has the same
* value as NaN, otherwise return false.
*
* @param v the float to compare
* @return whether the argument is NaN
*/
public static boolean isNaN(float v)
{
// This works since NaN != NaN is the only reflexive inequality
// comparison which returns true.
return v != v;
}
/**
* Return true if the float has a value
* equal to either NEGATIVE_INFINITY or
* POSITIVE_INFINITY, otherwise return false.
*
* @param v the float to compare
* @return whether the argument is (-/+) infinity
*/
public static boolean isInfinite(float v)
{
return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
}
/**
* Return true if the value of this Float
* is the same as NaN, otherwise return false.
*
* @return whether this Float is NaN
*/
public boolean isNaN()
{
return isNaN(value);
}
/**
* Return true if the value of this Float
* is the same as NEGATIVE_INFINITY or
* POSITIVE_INFINITY, otherwise return false.
*
* @return whether this Float is (-/+) infinity
*/
public boolean isInfinite()
{
return isInfinite(value);
}
/**
* Convert the float value of this Float
* to a String. This method calls
* Float.toString(float) to do its dirty work.
*
* @return the String representation
* @see #toString(float)
*/
public String toString()
{
return toString(value);
}
/**
* Return the value of this Float as a byte.
*
* @return the byte value
* @since 1.1
*/
public byte byteValue()
{
return (byte) value;
}
/**
* Return the value of this Float as a short.
*
* @return the short value
* @since 1.1
*/
public short shortValue()
{
return (short) value;
}
/**
* Return the value of this Integer as an int.
*
* @return the int value
*/
public int intValue()
{
return (int) value;
}
/**
* Return the value of this Integer as a long.
*
* @return the long value
*/
public long longValue()
{
return (long) value;
}
/**
* Return the value of this Float.
*
* @return the float value
*/
public float floatValue()
{
return value;
}
/**
* Return the value of this Float as a double
*
* @return the double value
*/
public double doubleValue()
{
return value;
}
/**
* Return a hashcode representing this Object. Float's hash
* code is calculated by calling floatToIntBits(floatValue()).
*
* @return this Object's hash code
* @see #floatToIntBits(float)
*/
public int hashCode()
{
return floatToIntBits(value);
}
/**
* Returns true if obj is an instance of
* Float and represents the same float value. Unlike comparing
* two floats with ==, this treats two instances of
* Float.NaN as equal, but treats 0.0 and
* -0.0 as unequal.
*
*
Note that f1.equals(f2) is identical to
* floatToIntBits(f1.floatValue()) ==
* floatToIntBits(f2.floatValue()).
*
* @param obj the object to compare
* @return whether the objects are semantically equal
*/
public boolean equals(Object obj)
{
if (! (obj instanceof Float))
return false;
float f = ((Float) obj).value;
// Avoid call to native method. However, some implementations, like gcj,
// are better off using floatToIntBits(value) == floatToIntBits(f).
// Check common case first, then check NaN and 0.
if (value == f)
return (value != 0) || (1 / value == 1 / f);
return isNaN(value) && isNaN(f);
}
/**
* Convert the float to the IEEE 754 floating-point "single format" bit
* layout. Bit 31 (the most significant) is the sign bit, bits 30-23
* (masked by 0x7f800000) represent the exponent, and bits 22-0
* (masked by 0x007fffff) are the mantissa. This function collapses all
* versions of NaN to 0x7fc00000. The result of this function can be used
* as the argument to Float.intBitsToFloat(int) to obtain the
* original float value.
*
* @param value the float to convert
* @return the bits of the float
* @see #intBitsToFloat(int)
*/
// GCJ LOCAL: We diverge from Classpath for efficiency.
public static native int floatToIntBits(float value);
// END GCJ LOCAL
/**
* Convert the float to the IEEE 754 floating-point "single format" bit
* layout. Bit 31 (the most significant) is the sign bit, bits 30-23
* (masked by 0x7f800000) represent the exponent, and bits 22-0
* (masked by 0x007fffff) are the mantissa. This function leaves NaN alone,
* rather than collapsing to a canonical value. The result of this function
* can be used as the argument to Float.intBitsToFloat(int) to
* obtain the original float value.
*
* @param value the float to convert
* @return the bits of the float
* @see #intBitsToFloat(int)
*/
// GCJ LOCAL: We diverge from Classpath for efficiency.
public static native int floatToRawIntBits(float value);
// END GCJ LOCAL
/**
* Convert the argument in IEEE 754 floating-point "single format" bit
* layout to the corresponding float. Bit 31 (the most significant) is the
* sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and
* bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves
* NaN alone, so that you can recover the bit pattern with
* Float.floatToRawIntBits(float).
*
* @param bits the bits to convert
* @return the float represented by the bits
* @see #floatToIntBits(float)
* @see #floatToRawIntBits(float)
*/
// GCJ LOCAL: We diverge from Classpath for efficiency.
public static native float intBitsToFloat(int bits);
// END GCJ LOCAL
/**
* Compare two Floats numerically by comparing their float
* values. The result is positive if the first is greater, negative if the
* second is greater, and 0 if the two are equal. However, this special
* cases NaN and signed zero as follows: NaN is considered greater than
* all other floats, including POSITIVE_INFINITY, and positive
* zero is considered greater than negative zero.
*
* @param f the Float to compare
* @return the comparison
* @since 1.2
*/
public int compareTo(Float f)
{
return compare(value, f.value);
}
/**
* Behaves like compareTo(Float) unless the Object
* is not an Float.
*
* @param o the object to compare
* @return the comparison
* @throws ClassCastException if the argument is not a Float
* @see #compareTo(Float)
* @see Comparable
* @since 1.2
*/
public int compareTo(Object o)
{
return compare(value, ((Float) o).value);
}
/**
* Behaves like new Float(x).compareTo(new Float(y)); in
* other words this compares two floats, special casing NaN and zero,
* without the overhead of objects.
*
* @param x the first float to compare
* @param y the second float to compare
* @return the comparison
* @since 1.4
*/
public static int compare(float x, float y)
{
if (isNaN(x))
return isNaN(y) ? 0 : 1;
if (isNaN(y))
return -1;
// recall that 0.0 == -0.0, so we convert to infinities and try again
if (x == 0 && y == 0)
return (int) (1 / x - 1 / y);
if (x == y)
return 0;
return x > y ? 1 : -1;
}
}