float.java

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/* Float.java -- object wrapper for float
   Copyright (C) 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath 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 for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

Linking this library statically or dynamically with other modules is
making a combined work based on this library.  Thus, the terms and
conditions of the GNU General Public License cover the whole
combination.

As a special exception, the copyright holders of this library give you
permission to link this library with independent modules to produce an
executable, regardless of the license terms of these independent
modules, and to copy and distribute the resulting executable under
terms of your choice, provided that you also meet, for each linked
independent module, the terms and conditions of the license of that
module.  An independent module is a module which is not derived from
or based on this library.  If you modify this library, you may extend
this exception to your version of the library, but you are not
obligated to do so.  If you do not wish to do so, delete this
exception statement from your version. */

package java.lang;

import org.jnode.vm.Unsafe;

/**
 * Instances of class <code>Float</code> represent primitive
 * <code>float</code> values.
 *
 * Additionally, this class provides various helper functions and variables
 * related to floats.
 *
 * @author Paul Fisher
 * @author Andrew Haley <[e-mail]>
 * @author Eric Blake <[e-mail]>
 * @since 1.0
 * @status updated to 1.4
 */
public final class Float extends Number implements Comparable {
	/**
	 * Compatible with JDK 1.0+.
	 */
	private static final long serialVersionUID = -2671257302660747028L;

	private static final int EXPONENT_MASK	= 0x7f800000;
	private static final int MANTISSA_MASK	= 0x007fffff;
	private static final int NAN_BITS		= 0x7fc00000;
	private static final int MAX_DIGITS = 10;

	/**
	 * The maximum positive value a <code>double</code> may represent
	 * is 3.4028235e+38f.
	 */
	public static final float MAX_VALUE = 3.4028235e+38f;

	/**
	 * The minimum positive value a <code>float</code> 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 <code>float</code> is represented by this
	 * <code>Class</code> object.
	 * @since 1.1
	 */
	public static final Class TYPE = Class.getPrimitiveClass('F');

	/**
	 * The immutable value of this Float.
	 *
	 * @serial the wrapped float
	 */
	private final float value;

	/**
	 * Create a <code>Float</code> from the primitive <code>float</code>
	 * specified.
	 *
	 * @param value the <code>float</code> argument
	 */
	public Float(float value) {
		this.value = value;
	}

	/**
	 * Create a <code>Float</code> from the primitive <code>double</code>
	 * specified.
	 *
	 * @param value the <code>double</code> argument
	 */
	public Float(double value) {
		this.value = (float)value;
	}

	/**
	 * Create a <code>Float</code> from the specified <code>String</code>.
	 * This method calls <code>Float.parseFloat()</code>.
	 *
	 * @param s the <code>String</code> to convert
	 * @throws NumberFormatException if <code>s</code> cannot be parsed as a
	 *         <code>float</code>
	 * @throws NullPointerException if <code>s</code> is null
	 * @see #parseFloat(String)
	 */
	public Float(String s) {
		value = parseFloat(s);
	}

	/**
	 * Convert the <code>float</code> to a <code>String</code>.
	 * Floating-point string representation is fairly complex: here is a
	 * rundown of the possible values.  "<code>[-]</code>" indicates that a
	 * negative sign will be printed if the value (or exponent) is negative.
	 * "<code>&lt;number&gt;</code>" means a string of digits ('0' to '9').
	 * "<code>&lt;digit&gt;</code>" means a single digit ('0' to '9').<br>
	 *
	 * <table border=1>
	 * <tr><th>Value of Float</th><th>String Representation</th></tr>
	 * <tr><td>[+-] 0</td> <td><code>[-]0.0</code></td></tr>
	 * <tr><td>Between [+-] 10<sup>-3</sup> and 10<sup>7</sup>, exclusive</td>
	 *     <td><code>[-]number.number</code></td></tr>
	 * <tr><td>Other numeric value</td>
	 *     <td><code>[-]&lt;digit&gt;.&lt;number&gt;
	 *          E[-]&lt;number&gt;</code></td></tr>
	 * <tr><td>[+-] infinity</td> <td><code>[-]Infinity</code></td></tr>
	 * <tr><td>NaN</td> <td><code>NaN</code></td></tr>
	 * </table>
	 *
	 * Yes, negative zero <em>is</em> a possible value.  Note that there is
	 * <em>always</em> a <code>.</code> and at least one digit printed after
	 * it: even if the number is 3, it will be printed as <code>3.0</code>.
	 * 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.
	 *
	 * <p>To create other output formats, use {@link java.text.NumberFormat}.
	 *
	 * @XXX specify where we are not in accord with the spec.
	 *
	 * @param f the <code>float</code> to convert
	 * @return the <code>String</code> representing the <code>float</code>
	 */
	public static String toString(float v) {
		if (isNaN(v))
			return "NaN";
		if (v == POSITIVE_INFINITY)
			return "Infinity";
		if (v == NEGATIVE_INFINITY)
			return "-Infinity";

		boolean negative = (floatToRawIntBits(v) & (1 << 31)) != 0;
		float m = negative ? -v : v;

		if (m == 0.0d)
			return negative ? "-0.0" : "0.0";

		StringBuffer result = new StringBuffer(MAX_DIGITS * 2);
		if (negative) {
			result.append('-');
		}

		if (m >= 1e-3 && m < 1e7) {
			int digit = (int)(m-0.5f);
			int digits = 0;
			result.append(digit);
			result.append('.');
			m -= digit;
			while ((m > 0.0f) && (digits < MAX_DIGITS)) {
				m *= 10.0f;
				digit = (int)(m-0.5f);
				m -= digit;
				result.append(digit);
				digits++;
			}
			if (digits == 0) {
				result.append('0');
			}
		} else {
			int exponent = (int) (Math.log(m) / Math.log(10.0d));
			float mantissa = (float)(m / Math.pow(10.0d, (double)exponent));
			result.append(toString(mantissa));
			result.append('E');
			result.append(Integer.toString(exponent));
		}

		return result.toString();
	}

	/**
	 * Creates a new <code>Float</code> object using the <code>String</code>.
	 *
	 * @param s the <code>String</code> to convert
	 * @return the new <code>Float</code>
	 * @throws NumberFormatException if <code>s</code> cannot be parsed as a
	 *         <code>float</code>
	 * @throws NullPointerException if <code>s</code> is null
	 * @see #parseFloat(String)
	 */
	public static Float valueOf(String s) {
		return new Float(parseFloat(s));
	}

	/**
	 * Parse the specified <code>String</code> as a <code>float</code>. The
	 * extended BNF grammar is as follows:<br>
	 * <pre>
	 * <em>DecodableString</em>:
	 *      ( [ <code>-</code> | <code>+</code> ] <code>NaN</code> )
	 *    | ( [ <code>-</code> | <code>+</code> ] <code>Infinity</code> )
	 *    | ( [ <code>-</code> | <code>+</code> ] <em>FloatingPoint</em>
	 *              [ <code>f</code> | <code>F</code> | <code>d</code>
	 *                | <code>D</code>] )
	 * <em>FloatingPoint</em>:
	 *      ( { <em>Digit</em> }+ [ <code>.</code> { <em>Digit</em> } ]
	 *              [ <em>Exponent</em> ] )
	 *    | ( <code>.</code> { <em>Digit</em> }+ [ <em>Exponent</em> ] )
	 * <em>Exponent</em>:
	 *      ( ( <code>e</code> | <code>E</code> )
	 *              [ <code>-</code> | <code>+</code> ] { <em>Digit</em> }+ )
	 * <em>Digit</em>: <em><code>'0'</code> through <code>'9'</code></em>
	 * </pre>
	 *
	 * <p>NaN and infinity are special cases, to allow parsing of the output
	 * of toString.  Otherwise, the result is determined by calculating
	 * <em>n * 10<sup>exponent</sup></em> 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.
	 *
	 * <p>If an unexpected character is found in the <code>String</code>, a
	 * <code>NumberFormatException</code> will be thrown.  Leading and trailing
	 * 'whitespace' is ignored via <code>String.trim()</code>, but spaces
	 * internal to the actual number are not allowed.
	 *
	 * <p>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 <code>String</code> to convert
	 * @return the <code>float</code> value of <code>s</code>
	 * @throws NumberFormatException if <code>s</code> cannot be parsed as a
	 *         <code>float</code>
	 * @throws NullPointerException if <code>s</code> is null
	 * @see #MIN_VALUE