531 lines
17 KiB
Java
531 lines
17 KiB
Java
/* Float.java -- object wrapper for float
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Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.lang;
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import gnu.classpath.Configuration;
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/**
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* Instances of class <code>Float</code> represent primitive
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* <code>float</code> values.
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*
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* Additionally, this class provides various helper functions and variables
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* related to floats.
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*
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* @author Paul Fisher
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* @author Andrew Haley <aph@cygnus.com>
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* @author Eric Blake <ebb9@email.byu.edu>
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* @since 1.0
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* @status updated to 1.4
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*/
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public final class Float extends Number implements Comparable
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{
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/**
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* Compatible with JDK 1.0+.
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*/
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private static final long serialVersionUID = -2671257302660747028L;
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/**
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* The maximum positive value a <code>double</code> may represent
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* is 3.4028235e+38f.
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*/
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public static final float MAX_VALUE = 3.4028235e+38f;
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/**
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* The minimum positive value a <code>float</code> may represent
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* is 1.4e-45.
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*/
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public static final float MIN_VALUE = 1.4e-45f;
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/**
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* The value of a float representation -1.0/0.0, negative infinity.
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*/
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public static final float NEGATIVE_INFINITY = -1.0f / 0.0f;
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/**
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* The value of a float representation 1.0/0.0, positive infinity.
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*/
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public static final float POSITIVE_INFINITY = 1.0f / 0.0f;
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/**
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* All IEEE 754 values of NaN have the same value in Java.
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*/
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public static final float NaN = 0.0f / 0.0f;
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/**
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* The primitive type <code>float</code> is represented by this
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* <code>Class</code> object.
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* @since 1.1
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*/
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public static final Class TYPE = VMClassLoader.getPrimitiveClass('F');
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/**
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* The immutable value of this Float.
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*
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* @serial the wrapped float
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*/
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private final float value;
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/**
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* Load native routines necessary for this class.
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*/
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static
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{
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if (Configuration.INIT_LOAD_LIBRARY)
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{
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System.loadLibrary("javalang");
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}
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}
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/**
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* Create a <code>Float</code> from the primitive <code>float</code>
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* specified.
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*
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* @param value the <code>float</code> argument
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*/
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public Float(float value)
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{
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this.value = value;
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}
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/**
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* Create a <code>Float</code> from the primitive <code>double</code>
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* specified.
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*
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* @param value the <code>double</code> argument
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*/
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public Float(double value)
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{
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this.value = (float) value;
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}
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/**
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* Create a <code>Float</code> from the specified <code>String</code>.
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* This method calls <code>Float.parseFloat()</code>.
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*
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* @param s the <code>String</code> to convert
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* @throws NumberFormatException if <code>s</code> cannot be parsed as a
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* <code>float</code>
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* @throws NullPointerException if <code>s</code> is null
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* @see #parseFloat(String)
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*/
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public Float(String s)
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{
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value = parseFloat(s);
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}
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/**
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* Convert the <code>float</code> to a <code>String</code>.
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* Floating-point string representation is fairly complex: here is a
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* rundown of the possible values. "<code>[-]</code>" indicates that a
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* negative sign will be printed if the value (or exponent) is negative.
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* "<code><number></code>" means a string of digits ('0' to '9').
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* "<code><digit></code>" means a single digit ('0' to '9').<br>
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*
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* <table border=1>
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* <tr><th>Value of Float</th><th>String Representation</th></tr>
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* <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr>
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* <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td>
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* <td><code>[-]number.number</code></td></tr>
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* <tr><td>Other numeric value</td>
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* <td><code>[-]<digit>.<number>
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* E[-]<number></code></td></tr>
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* <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr>
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* <tr><td>NaN</td> <td><code>NaN</code></td></tr>
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* </table>
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*
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* Yes, negative zero <em>is</em> a possible value. Note that there is
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* <em>always</em> a <code>.</code> and at least one digit printed after
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* it: even if the number is 3, it will be printed as <code>3.0</code>.
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* After the ".", all digits will be printed except trailing zeros. The
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* result is rounded to the shortest decimal number which will parse back
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* to the same float.
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*
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* <p>To create other output formats, use {@link java.text.NumberFormat}.
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*
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* @XXX specify where we are not in accord with the spec.
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*
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* @param f the <code>float</code> to convert
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* @return the <code>String</code> representing the <code>float</code>
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*/
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public static String toString(float f)
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{
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return Double.toString(f, true);
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}
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/**
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* Creates a new <code>Float</code> object using the <code>String</code>.
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*
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* @param s the <code>String</code> to convert
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* @return the new <code>Float</code>
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* @throws NumberFormatException if <code>s</code> cannot be parsed as a
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* <code>float</code>
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* @throws NullPointerException if <code>s</code> is null
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* @see #parseFloat(String)
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*/
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public static Float valueOf(String s)
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{
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return new Float(parseFloat(s));
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}
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/**
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* Parse the specified <code>String</code> as a <code>float</code>. The
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* extended BNF grammar is as follows:<br>
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* <pre>
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* <em>DecodableString</em>:
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* ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
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* | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
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* | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
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* [ <code>f</code> | <code>F</code> | <code>d</code>
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* | <code>D</code>] )
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* <em>FloatingPoint</em>:
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* ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
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* [ <em>Exponent</em> ] )
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* | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
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* <em>Exponent</em>:
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* ( ( <code>e</code> | <code>E</code> )
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* [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
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* <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
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* </pre>
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*
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* <p>NaN and infinity are special cases, to allow parsing of the output
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* of toString. Otherwise, the result is determined by calculating
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* <em>n * 10<sup>exponent</sup></em> to infinite precision, then rounding
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* to the nearest float. Remember that many numbers cannot be precisely
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* represented in floating point. In case of overflow, infinity is used,
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* and in case of underflow, signed zero is used. Unlike Integer.parseInt,
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* this does not accept Unicode digits outside the ASCII range.
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*
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* <p>If an unexpected character is found in the <code>String</code>, a
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* <code>NumberFormatException</code> will be thrown. Leading and trailing
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* 'whitespace' is ignored via <code>String.trim()</code>, but spaces
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* internal to the actual number are not allowed.
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*
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* <p>To parse numbers according to another format, consider using
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* {@link java.text.NumberFormat}.
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*
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* @XXX specify where/how we are not in accord with the spec.
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*
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* @param str the <code>String</code> to convert
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* @return the <code>float</code> value of <code>s</code>
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* @throws NumberFormatException if <code>s</code> cannot be parsed as a
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* <code>float</code>
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* @throws NullPointerException if <code>s</code> is null
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* @see #MIN_VALUE
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* @see #MAX_VALUE
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* @see #POSITIVE_INFINITY
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* @see #NEGATIVE_INFINITY
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* @since 1.2
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*/
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public static float parseFloat(String s)
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{
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// XXX Rounding parseDouble() causes some errors greater than 1 ulp from
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// the infinitely precise decimal.
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return (float) Double.parseDouble(s);
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}
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/**
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* Return <code>true</code> if the <code>float</code> has the same
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* value as <code>NaN</code>, otherwise return <code>false</code>.
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*
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* @param v the <code>float</code> to compare
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* @return whether the argument is <code>NaN</code>
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*/
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public static boolean isNaN(float v)
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{
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// This works since NaN != NaN is the only reflexive inequality
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// comparison which returns true.
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return v != v;
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}
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/**
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* Return <code>true</code> if the <code>float</code> has a value
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* equal to either <code>NEGATIVE_INFINITY</code> or
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* <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
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*
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* @param v the <code>float</code> to compare
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* @return whether the argument is (-/+) infinity
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*/
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public static boolean isInfinite(float v)
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{
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return v == POSITIVE_INFINITY || v == NEGATIVE_INFINITY;
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}
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/**
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* Return <code>true</code> if the value of this <code>Float</code>
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* is the same as <code>NaN</code>, otherwise return <code>false</code>.
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*
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* @return whether this <code>Float</code> is <code>NaN</code>
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*/
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public boolean isNaN()
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{
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return isNaN(value);
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}
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/**
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* Return <code>true</code> if the value of this <code>Float</code>
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* is the same as <code>NEGATIVE_INFINITY</code> or
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* <code>POSITIVE_INFINITY</code>, otherwise return <code>false</code>.
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*
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* @return whether this <code>Float</code> is (-/+) infinity
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*/
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public boolean isInfinite()
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{
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return isInfinite(value);
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}
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/**
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* Convert the <code>float</code> value of this <code>Float</code>
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* to a <code>String</code>. This method calls
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* <code>Float.toString(float)</code> to do its dirty work.
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*
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* @return the <code>String</code> representation
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* @see #toString(float)
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*/
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public String toString()
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{
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return toString(value);
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}
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/**
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* Return the value of this <code>Float</code> as a <code>byte</code>.
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*
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* @return the byte value
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* @since 1.1
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*/
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public byte byteValue()
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{
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return (byte) value;
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}
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/**
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* Return the value of this <code>Float</code> as a <code>short</code>.
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*
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* @return the short value
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* @since 1.1
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*/
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public short shortValue()
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{
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return (short) value;
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}
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/**
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* Return the value of this <code>Integer</code> as an <code>int</code>.
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*
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* @return the int value
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*/
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public int intValue()
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{
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return (int) value;
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}
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/**
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* Return the value of this <code>Integer</code> as a <code>long</code>.
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*
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* @return the long value
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*/
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public long longValue()
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{
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return (long) value;
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}
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/**
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* Return the value of this <code>Float</code>.
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*
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* @return the float value
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*/
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public float floatValue()
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{
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return value;
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}
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/**
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* Return the value of this <code>Float</code> as a <code>double</code>
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*
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* @return the double value
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*/
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public double doubleValue()
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{
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return value;
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}
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/**
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* Return a hashcode representing this Object. <code>Float</code>'s hash
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* code is calculated by calling <code>floatToIntBits(floatValue())</code>.
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*
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* @return this Object's hash code
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* @see #floatToIntBits(float)
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*/
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public int hashCode()
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{
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return floatToIntBits(value);
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}
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/**
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* Returns <code>true</code> if <code>obj</code> is an instance of
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* <code>Float</code> and represents the same float value. Unlike comparing
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* two floats with <code>==</code>, this treats two instances of
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* <code>Float.NaN</code> as equal, but treats <code>0.0</code> and
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* <code>-0.0</code> as unequal.
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*
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* <p>Note that <code>f1.equals(f2)<code> is identical to
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* <code>floatToIntBits(f1.floatValue()) ==
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* floatToIntBits(f2.floatValue())<code>.
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*
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* @param obj the object to compare
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* @return whether the objects are semantically equal
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*/
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public boolean equals(Object obj)
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{
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if (! (obj instanceof Float))
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return false;
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float f = ((Float) obj).value;
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// Avoid call to native method. However, some implementations, like gcj,
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// are better off using floatToIntBits(value) == floatToIntBits(f).
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// Check common case first, then check NaN and 0.
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if (value == f)
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return (value != 0) || (1 / value == 1 / f);
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return isNaN(value) && isNaN(f);
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}
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/**
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* Convert the float to the IEEE 754 floating-point "single format" bit
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* layout. Bit 31 (the most significant) is the sign bit, bits 30-23
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* (masked by 0x7f800000) represent the exponent, and bits 22-0
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* (masked by 0x007fffff) are the mantissa. This function collapses all
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* versions of NaN to 0x7fc00000. The result of this function can be used
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* as the argument to <code>Float.intBitsToFloat(int)</code> to obtain the
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* original <code>float</code> value.
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*
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* @param value the <code>float</code> to convert
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* @return the bits of the <code>float</code>
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* @see #intBitsToFloat(int)
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*/
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public static native int floatToIntBits(float value);
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/**
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* Convert the float to the IEEE 754 floating-point "single format" bit
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* layout. Bit 31 (the most significant) is the sign bit, bits 30-23
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* (masked by 0x7f800000) represent the exponent, and bits 22-0
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* (masked by 0x007fffff) are the mantissa. This function leaves NaN alone,
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* rather than collapsing to a canonical value. The result of this function
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* can be used as the argument to <code>Float.intBitsToFloat(int)</code> to
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* obtain the original <code>float</code> value.
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*
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* @param value the <code>float</code> to convert
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* @return the bits of the <code>float</code>
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* @see #intBitsToFloat(int)
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*/
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public static native int floatToRawIntBits(float value);
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/**
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* Convert the argument in IEEE 754 floating-point "single format" bit
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* layout to the corresponding float. Bit 31 (the most significant) is the
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* sign bit, bits 30-23 (masked by 0x7f800000) represent the exponent, and
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* bits 22-0 (masked by 0x007fffff) are the mantissa. This function leaves
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* NaN alone, so that you can recover the bit pattern with
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* <code>Float.floatToRawIntBits(float)</code>.
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*
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* @param bits the bits to convert
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* @return the <code>float</code> represented by the bits
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* @see #floatToIntBits(float)
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* @see #floatToRawIntBits(float)
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*/
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public static native float intBitsToFloat(int bits);
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/**
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* Compare two Floats numerically by comparing their <code>float</code>
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* values. The result is positive if the first is greater, negative if the
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* second is greater, and 0 if the two are equal. However, this special
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* cases NaN and signed zero as follows: NaN is considered greater than
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* all other floats, including <code>POSITIVE_INFINITY</code>, and positive
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* zero is considered greater than negative zero.
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*
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* @param f the Float to compare
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* @return the comparison
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* @since 1.2
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*/
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public int compareTo(Float f)
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{
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return compare(value, f.value);
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}
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/**
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* Behaves like <code>compareTo(Float)</code> unless the Object
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* is not an <code>Float</code>.
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|
*
|
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* @param o the object to compare
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* @return the comparison
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* @throws ClassCastException if the argument is not a <code>Float</code>
|
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* @see #compareTo(Float)
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* @see Comparable
|
|
* @since 1.2
|
|
*/
|
|
public int compareTo(Object o)
|
|
{
|
|
return compare(value, ((Float) o).value);
|
|
}
|
|
|
|
/**
|
|
* Behaves like <code>new Float(x).compareTo(new Float(y))</code>; 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;
|
|
}
|
|
}
|