/*
* @(#)Float.java 1.69 06/10/10
*
* Copyright 1990-2008 Sun Microsystems, Inc. All Rights Reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version
* 2 only, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License version 2 for more details (a copy is
* included at /legal/license.txt).
*
* You should have received a copy of the GNU General Public License
* version 2 along with this work; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*
* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
* information or have any questions.
*
*/
package java.lang;
/**
* The <code>Float</code> class wraps a value of primitive type
* <code>float</code> in an object. An object of type
* <code>Float</code> contains a single field whose type is
* <code>float</code>.
* <p>
* In addition, this class provides several methods for converting a
* <code>float</code> to a <code>String</code> and a
* <code>String</code> to a <code>float</code>, as well as other
* constants and methods useful when dealing with a
* <code>float</code>.
*
* @author Lee Boynton
* @author Arthur van Hoff
* @version 1.80, 01/23/03
* @since JDK1.0
*/
public final class Float extends Number implements Comparable {
/**
* A constant holding the positive infinity of type
* <code>float</code>. It is equal to the value returned by
* <code>Float.intBitsToFloat(0x7f800000)</code>.
*/
public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
/**
* A constant holding the negative infinity of type
* <code>float</code>. It is equal to the value returned by
* <code>Float.intBitsToFloat(0xff800000)</code>.
*/
public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
/**
* A constant holding a Not-a-Number (NaN) value of type
* <code>float</code>. It is equivalent to the value returned by
* <code>Float.intBitsToFloat(0x7fc00000)</code>.
*/
public static final float NaN = 0.0f / 0.0f;
/**
* A constant holding the largest positive finite value of type
* <code>float</code>, (2-2<sup>-23</sup>)·2<sup>127</sup>.
* It is equal to the value returned by
* <code>Float.intBitsToFloat(0x7f7fffff)</code>.
*/
public static final float MAX_VALUE = 3.4028235e+38f;
/**
* A constant holding the smallest positive nonzero value of type
* <code>float</code>, 2<sup>-149</sup>. It is equal to the value
* returned by <code>Float.intBitsToFloat(0x1)</code>.
*/
public static final float MIN_VALUE = 1.4e-45f;
/**
* The <code>Class</code> instance representing the primitive type
* <code>float</code>.
*
* @since JDK1.1
*/
public static final Class TYPE = Class.getPrimitiveClass("float");
/**
* Returns a string representation of the <code>float</code>
* argument. All characters mentioned below are ASCII characters.
* <ul>
* <li>If the argument is NaN, the result is the string
* "<code>NaN</code>".
* <li>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>-</code>' (<code>'\u002D'</code>); if the sign is
* positive, no sign character appears in the result. As for
* the magnitude <i>m</i>:
* <ul>
* <li>If <i>m</i> is infinity, it is represented by the characters
* <code>"Infinity"</code>; thus, positive infinity produces
* the result <code>"Infinity"</code> and negative infinity
* produces the result <code>"-Infinity"</code>.
* <li>If <i>m</i> is zero, it is represented by the characters
* <code>"0.0"</code>; thus, negative zero produces the result
* <code>"-0.0"</code> and positive zero produces the result
* <code>"0.0"</code>.
* <li> If <i>m</i> is greater than or equal to 10<sup>-3</sup> but
* less than 10<sup>7</sup>, then it is represented as the
* integer part of <i>m</i>, in decimal form with no leading
* zeroes, followed by '<code>.</code>'
* (<code>'\u002E'</code>), followed by one or more
* decimal digits representing the fractional part of
* <i>m</i>.
* <li> If <i>m</i> is less than 10<sup>-3</sup> or greater than or
* equal to 10<sup>7</sup>, then it is represented in
* so-called "computerized scientific notation." Let <i>n</i>
* be the unique integer such that 10<sup><i>n</i> </sup><=
* <i>m</i> < 10<sup><i>n</i>+1</sup>; then let <i>a</i>
* be the mathematically exact quotient of <i>m</i> and
* 10<sup><i>n</i></sup> so that 1 <= <i>a</i> < 10.
* The magnitude is then represented as the integer part of
* <i>a</i>, as a single decimal digit, followed by
* '<code>.</code>' (<code>'\u002E'</code>), followed by
* decimal digits representing the fractional part of
* <i>a</i>, followed by the letter '<code>E</code>'
* (<code>'\u0045'</code>), followed by a representation
* of <i>n</i> as a decimal integer, as produced by the
* method <code>{@link
* java.lang.Integer#toString(int)}</code>.
* </ul>
* </ul>
* How many digits must be printed for the fractional part of
* <i>m</i> or <i>a</i>? 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</code>. That is, suppose that <i>x</i> is the
* exact mathematical value represented by the decimal
* representation produced by this method for a finite nonzero
* argument <i>f</i>. Then <i>f</i> must be the <code>float</code>
* value nearest to <i>x</i>; or, if two <code>float</code> values are
* equally close to <i>x</i>, then <i>f</i> must be one of
* them and the least significant bit of the significand of
* <i>f</i> must be <code>0</code>.
* <p>
* To create localized string representations of a floating-point
* value, use subclasses of {@link java.text.NumberFormat}.
*
* @param f the float to be converted.
* @return a string representation of the argument.
*/
public static String toString(float f) {
return new FloatingDecimal(f).toJavaFormatString();
}
/**
* Returns a <code>Float</code> object holding the
* <code>float</code> value represented by the argument string
* <code>s</code>.
* <p>
* If <code>s</code> is <code>null</code>, then a
* <code>NullPointerException</code> is thrown.
* <p>
* Leading and trailing whitespace characters in <code>s</code>
* are ignored. The rest of <code>s</code> should constitute a
* <i>FloatValue</i> as described by the lexical syntax rules:
* <blockquote><i>
* <dl>
* <dt>FloatValue:
* <dd><i>Sign<sub>opt</sub></i> <code>NaN</code>
* <dd><i>Sign<sub>opt</sub></i> <code>Infinity</code>
* <dd>Sign<sub>opt</sub> FloatingPointLiteral
* </dl>
* </i></blockquote>
* where <i>Sign</i> and <i>FloatingPointLiteral</i> are as
* defined in <a href="http://java.sun.com/docs/books/jls/second_edition/html/lexical.doc.html#230798">§3.10.2</a>
* of the <a href="http://java.sun.com/docs/books/jls/html/">Java
* Language Specification</a>. If <code>s</code> does not have the
* form of a <i>FloatValue</i>, then a
* <code>NumberFormatException</code> is thrown. Otherwise,
* <code>s</code> is regarded as representing an exact decimal
* value in the usual "computerized scientific notation"; this
* exact decimal value is then conceptually converted to an
* "infinitely precise" binary value that is then rounded to type
* <code>float</code> by the usual round-to-nearest rule of IEEE
* 754 floating-point arithmetic, which includes preserving the
* sign of a zero value. Finally, a <code>Float</code> object
* representing this <code>float</code> value is returned.
* <p>
* To interpret localized string representations of a
* floating-point value, use subclasses of {@link
* java.text.NumberFormat}.
*
* <p>Note that trailing format specifiers, specifiers that
* determine the type of a floating-point literal
* (<code>1.0f</code> is a <code>float</code> value;
* <code>1.0d</code> is a <code>double</code> value), do
* <em>not</em> 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</code>
* followed by <code>double</code> to <code>float</code>, is
* <em>not</em> equivalent to converting a string directly to
* <code>float</code>. For example, if first converted to an
* intermediate <code>double</code> and then to
* <code>float</code>, the string<br>
* <code>"1.00000017881393421514957253748434595763683319091796875001d"</code><br>
* results in the <code>float</code> value
* <code>1.0000002f</code>; if the string is converted directly to
* <code>float</code>, <code>1.000000<b>1</b>f</code> results.
*
* @param s the string to be parsed.
* @return a <code>Float</code> object holding the value
* represented by the <code>String</code> argument.
* @exception NumberFormatException if the string does not contain a
* parsable number.
*/
public static Float valueOf(String s) throws NumberFormatException {
return new Float(FloatingDecimal.readJavaFormatString(s).floatValue());
}
/**
* Returns a new <code>float</code> initialized to the value
* represented by the specified <code>String</code>, as performed
* by the <code>valueOf</code> method of class <code>Float</code>.
*
* @param s the string to be parsed.
* @return the <code>float</code> value represented by the string
* argument.
* @exception NumberFormatException if the string does not contain a
* parsable <code>float</code>.
* @see java.lang.Float#valueOf(String)
* @since 1.2
*/
public static float parseFloat(String s) throws NumberFormatException {
return FloatingDecimal.readJavaFormatString(s).floatValue();
}
/**
* Returns <code>true</code> if the specified number is a
* Not-a-Number (NaN) value, <code>false</code> otherwise.
*
* @param v the value to be tested.
* @return <code>true</code> if the argument is NaN;
* <code>false</code> otherwise.
*/
static public boolean isNaN(float v) {
return (v != v);
}
/**
* Returns <code>true</code> if the specified number is infinitely
* large in magnitude, <code>false</code> otherwise.
*
* @param v the value to be tested.
* @return <code>true</code> if the argument is positive infinity or
* negative infinity; <code>false</code> otherwise.
*/
static public boolean isInfinite(float v) {
return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
}
/**
* The value of the Float.
*
* @serial
*/
private float value;
/**
* Constructs a newly allocated <code>Float</code> object that
* represents the primitive <code>float</code> argument.
*
* @param value the value to be represented by the <code>Float</code>.
*/
public Float(float value) {
this.value = value;
}
/**
* Constructs a newly allocated <code>Float</code> object that
* represents the argument converted to type <code>float</code>.
*
* @param value the value to be represented by the <code>Float</code>.
*/
public Float(double value) {
this.value = (float)value;
}
/**
* Constructs a newly allocated <code>Float</code> object that
* represents the floating-point value of type <code>float</code>
* represented by the string. The string is converted to a
* <code>float</code> value as if by the <code>valueOf</code> method.
*
* @param s a string to be converted to a <code>Float</code>.
* @exception NumberFormatException if the string does not contain a
* parsable number.
* @see java.lang.Float#valueOf(java.lang.String)
*/
public Float(String s) throws NumberFormatException {
// TODO: this is inefficient
this(valueOf(s).floatValue());
}
/**
* Returns <code>true</code> if this <code>Float</code> value is a
* Not-a-Number (NaN), <code>false</code> otherwise.
*
* @return <code>true</code> if the value represented by this object is
* NaN; <code>false</code> otherwise.
*/
public boolean isNaN() {
return isNaN(value);
}
/**
* Returns <code>true</code> if this <code>Float</code> value is
* infinitely large in magnitude, <code>false</code> otherwise.
*
* @return <code>true</code> if the value represented by this object is
* positive infinity or negative infinity;
* <code>false</code> otherwise.
*/
public boolean isInfinite() {
return isInfinite(value);
}
/**
* Returns a string representation of this <code>Float</code> object.
* The primitive <code>float</code> value represented by this object
* is converted to a <code>String</code> exactly as if by the method
* <code>toString</code> of one argument.
*
* @return a <code>String</code> representation of this object.
* @see java.lang.Float#toString(float)
*/
public String toString() {
return String.valueOf(value);
}
/**
* Returns the value of this <code>Float</code> as a
* <code>byte</code> (by casting to a <code>byte</code>).
*
* @return the <code>float</code> value represented by this object
* converted to type <code>byte</code>
*/
public byte byteValue() {
return (byte)value;
}
/**
* Returns the value of this <code>Float</code> as a
* <code>short</code> (by casting to a <code>short</code>).
*
* @return the <code>float</code> value represented by this object
* converted to type <code>short</code>
* @since JDK1.1
*/
public short shortValue() {
return (short)value;
}
/**
* Returns the value of this <code>Float</code> as an
* <code>int</code> (by casting to type <code>int</code>).
*
* @return the <code>float</code> value represented by this object
* converted to type <code>int</code>
*/
public int intValue() {
return (int)value;
}
/**
* Returns value of this <code>Float</code> as a <code>long</code>
* (by casting to type <code>long</code>).
*
* @return the <code>float</code> value represented by this object
* converted to type <code>long</code>
*/
public long longValue() {
return (long)value;
}
/**
* Returns the <code>float</code> value of this <code>Float</code>
* object.
*
* @return the <code>float</code> value represented by this object
*/
public float floatValue() {
return value;
}
/**
* Returns the <code>double</code> value of this
* <code>Float</code> object.
*
* @return the <code>float</code> value represented by this
* object is converted to type <code>double</code> and the
* result of the conversion is returned.
*/
public double doubleValue() {
return (double)value;
}
/**
* Returns a hash code for this <code>Float</code> object. The
* result is the integer bit representation, exactly as produced
* by the method {@link #floatToIntBits(float)}, of the primitive
* <code>float</code> value represented by this <code>Float</code>
* object.
*
* @return a hash code value for this object.
*/
public int hashCode() {
return floatToIntBits(value);
}
/**
* Compares this object against the specified object. The result
* is <code>true</code> if and only if the argument is not
* <code>null</code> and is a <code>Float</code> object that
* represents a <code>float</code> with the same value as the
* <code>float</code> represented by this object. For this
* purpose, two <code>float</code> values are considered to be the
* same if and only if the method {@link #floatToIntBits(float)}
* returns the identical <code>int</code> value when applied to
* each.
* <p>
* Note that in most cases, for two instances of class
* <code>Float</code>, <code>f1</code> and <code>f2</code>, the value
* of <code>f1.equals(f2)</code> is <code>true</code> if and only if
* <blockquote><pre>
* f1.floatValue() == f2.floatValue()
* </pre></blockquote>
* <p>
* also has the value <code>true</code>. However, there are two exceptions:
* <ul>
* <li>If <code>f1</code> and <code>f2</code> both represent
* <code>Float.NaN</code>, then the <code>equals</code> method returns
* <code>true</code>, even though <code>Float.NaN==Float.NaN</code>
* has the value <code>false</code>.
* <li>If <code>f1</code> represents <code>+0.0f</code> while
* <code>f2</code> represents <code>-0.0f</code>, or vice
* versa, the <code>equal</code> test has the value
* <code>false</code>, even though <code>0.0f==-0.0f</code>
* has the value <code>true</code>.
* </ul>
* This definition allows hash tables to operate properly.
*
* @param obj the object to be compared
* @return <code>true</code> if the objects are the same;
* <code>false</code> otherwise.
* @see java.lang.Float#floatToIntBits(float)
*/
public boolean equals(Object obj) {
return (obj instanceof Float)
&& (floatToIntBits(((Float)obj).value) == floatToIntBits(value));
}
/**
* Returns a representation of the specified floating-point value
* according to the IEEE 754 floating-point "single format" bit
* layout.
* <p>
* Bit 31 (the bit that is selected by the mask
* <code>0x80000000</code>) represents the sign of the floating-point
* number.
* Bits 30-23 (the bits that are selected by the mask
* <code>0x7f800000</code>) represent the exponent.
* Bits 22-0 (the bits that are selected by the mask
* <code>0x007fffff</code>) represent the significand (sometimes called
* the mantissa) of the floating-point number.
* <p>If the argument is positive infinity, the result is
* <code>0x7f800000</code>.
* <p>If the argument is negative infinity, the result is
* <code>0xff800000</code>.
* <p>If the argument is NaN, the result is <code>0x7fc00000</code>.
* <p>
* In all cases, the result is an integer that, when given to the
* {@link #intBitsToFloat(int)} method, will produce a floating-point
* value the same as the argument to <code>floatToIntBits</code>
* (except all NaN values are collapsed to a single
* "canonical" NaN value).
*
* @param value a floating-point number.
* @return the bits that represent the floating-point number.
*/
public static native int floatToIntBits(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.
* <p>
* Bit 31 (the bit that is selected by the mask
* <code>0x80000000</code>) represents the sign of the floating-point
* number.
* Bits 30-23 (the bits that are selected by the mask
* <code>0x7f800000</code>) represent the exponent.
* Bits 22-0 (the bits that are selected by the mask
* <code>0x007fffff</code>) represent the significand (sometimes called
* the mantissa) of the floating-point number.
* <p>If the argument is positive infinity, the result is
* <code>0x7f800000</code>.
* <p>If the argument is negative infinity, the result is
* <code>0xff800000</code>.
* <p>
* If the argument is NaN, the result is the integer representing
* the actual NaN value. Unlike the <code>floatToIntBits</code>
* method, <code>intToRawIntBits</code> does not collapse all the
* bit patterns encoding a NaN to a single "canonical"
* NaN value.
* <p>
* In all cases, the result is an integer that, when given to the
* {@link #intBitsToFloat(int)} method, will produce a
* floating-point value the same as the argument to
* <code>floatToRawIntBits</code>.
* @param value a floating-point number.
* @return the bits that represent the floating-point number.
*/
public static native int floatToRawIntBits(float value);
/**
* Returns the <code>float</code> value 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 format" bit layout.
* <p>
* If the argument is <code>0x7f800000</code>, the result is positive
* infinity.
* <p>
* If the argument is <code>0xff800000</code>, the result is negative
* infinity.
* <p>
* If the argument is any value in the range
* <code>0x7f800001</code> through <code>0x7fffffff</code> or in
* the range <code>0xff800001</code> through
* <code>0xffffffff</code>, 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</code> method.
* <p>
* In all other cases, let <i>s</i>, <i>e</i>, and <i>m</i> be three
* values that can be computed from the argument:
* <blockquote><pre>
* int s = ((bits >> 31) == 0) ? 1 : -1;
* int e = ((bits >> 23) & 0xff);
* int m = (e == 0) ?
* (bits & 0x7fffff) << 1 :
* (bits & 0x7fffff) | 0x800000;
* </pre></blockquote>
* Then the floating-point result equals the value of the mathematical
* expression <i>s</i>·<i>m</i>·2<sup><i>e</i>-150</sup>.
*<p>
* Note that this method may not be able to return a
* <code>float</code> NaN with exactly same bit pattern as the
* <code>int</code> argument. IEEE 754 distinguishes between two
* kinds of NaNs, quiet NaNs and <i>signaling NaNs</i>. 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</code> may
* not be able to return a <code>float</code> with a signaling NaN
* bit pattern. Consequently, for some <code>int</code> values,
* <code>floatToRawIntBits(intBitsToFloat(start))</code> may
* <i>not</i> equal <code>start</code>. 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.
*
* @param bits an integer.
* @return the <code>float</code> floating-point value with the same bit
* pattern.
*/
public static native float intBitsToFloat(int bits);
/**
* Compares two <code>Float</code> 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><, <=, ==, >= ></code>) when
* applied to primitive <code>float</code> values:
* <ul><li>
* <code>Float.NaN</code> is considered by this method to
* be equal to itself and greater than all other
* <code>float</code> values
* (including <code>Float.POSITIVE_INFINITY</code>).
* <li>
* <code>0.0f</code> is considered by this method to be greater
* than <code>-0.0f</code>.
* </ul>
* This ensures that <code>Float.compareTo(Object)</code> (which
* forwards its behavior to this method) obeys the general
* contract for <code>Comparable.compareTo</code>, and that the
* <i>natural order</i> on <code>Float</code>s is <i>consistent
* with equals</i>.
*
* @param anotherFloat the <code>Float</code> to be compared.
* @return the value <code>0</code> if <code>anotherFloat</code> is
* numerically equal to this <code>Float</code>; a value
* less than <code>0</code> if this <code>Float</code>
* is numerically less than <code>anotherFloat</code>;
* and a value greater than <code>0</code> if this
* <code>Float</code> is numerically greater than
* <code>anotherFloat</code>.
*
* @since 1.2
* @see Comparable#compareTo(Object)
*/
public int compareTo(Float anotherFloat) {
return Float.compare(value, anotherFloat.value);
}
/**
* Compares this <code>Float</code> object to another object. If
* the object is a <code>Float</code>, this function behaves like
* <code>compareTo(Float)</code>. Otherwise, it throws a
* <code>ClassCastException</code> (as <code>Float</code> objects
* are comparable only to other <code>Float</code> objects).
*
* @param o the <code>Object</code> to be compared.
* @return the value <code>0</code> if the argument is a
* <code>Float</code> numerically equal to this
* <code>Float</code>; a value less than <code>0</code>
* if the argument is a <code>Float</code> numerically
* greater than this <code>Float</code>; and a value
* greater than <code>0</code> if the argument is a
* <code>Float</code> numerically less than this
* <code>Float</code> .
* @exception <code>ClassCastException</code> if the argument is not a
* <code>Float</code>.
* @see java.lang.Comparable
* @since 1.2
*/
public int compareTo(Object o) {
return compareTo((Float)o);
}
/**
* Compares the two specified <code>float</code> values. The sign
* of the integer value returned is the same as that of the
* integer that would be returned by the call:
* <pre>
* new Float(f1).compareTo(new Float(f2))
* </pre>
*
* @param f1 the first <code>float</code> to compare.
* @param f2 the second <code>float</code> to compare.
* @return the value <code>0</code> if <code>f1</code> is
* numerically equal to <code>f2</code>; a value less than
* <code>0</code> if <code>f1</code> is numerically less than
* <code>f2</code>; and a value greater than <code>0</code>
* if <code>f1</code> is numerically greater than
* <code>f2</code>.
* @since 1.4
*/
public static int compare(float f1, float f2) {
if (f1 < f2)
return -1; // Neither val is NaN, thisVal is smaller
if (f1 > f2)
return 1; // Neither val is NaN, thisVal is larger
int thisBits = Float.floatToIntBits(f1);
int anotherBits = Float.floatToIntBits(f2);
return (thisBits == anotherBits ? 0 : // Values are equal
(thisBits < anotherBits ? -1 : // (-0.0, 0.0) or (!NaN, NaN)
1)); // (0.0, -0.0) or (NaN, !NaN)
}
/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = -2671257302660747028L;
}