double.java

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/*
 * @(#)Double.java	1.73 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>Double</code> class wraps a value of the primitive type
 * <code>double</code> in an object. An object of type
 * <code>Double</code> contains a single field whose type is
 * <code>double</code>.
 * <p>
 * In addition, this class provides several methods for converting a
 * <code>double</code> to a <code>String</code> and a
 * <code>String</code> to a <code>double</code>, as well as other
 * constants and methods useful when dealing with a
 * <code>double</code>.
 *
 * @version 1.82, 01/23/03
 * @since JDK1.0
 */
public final class Double extends Number implements Comparable {
    /**
     * A constant holding the positive infinity of type
     * <code>double</code>. It is equal to the value returned by
     * <code>Double.longBitsToDouble(0x7ff0000000000000L)</code>.
     */
    public static final double POSITIVE_INFINITY = 1.0 / 0.0;

    /**
     * A constant holding the negative infinity of type
     * <code>double</code>. It is equal to the value returned by
     * <code>Double.longBitsToDouble(0xfff0000000000000L)</code>.
     */
    public static final double NEGATIVE_INFINITY = -1.0 / 0.0;

    /** 
     * A constant holding a Not-a-Number (NaN) value of type
     * <code>double</code>. It is equivalent to the value returned by
     * <code>Double.longBitsToDouble(0x7ff8000000000000L)</code>.
     */
    public static final double NaN = 0.0d / 0.0;

    /**
     * A constant holding the largest positive finite value of type
     * <code>double</code>, (2-2<sup>-52</sup>)&middot;2<sup>1023</sup>.
     * It is equal to the value returned by:
     * <code>Double.longBitsToDouble(0x7fefffffffffffffL)</code>.
     */
    public static final double MAX_VALUE = 1.7976931348623157e+308;

    /**
     * A constant holding the smallest positive nonzero value of type
     * <code>double</code>, 2<sup>-1074</sup>. It is equal to the
     * value returned by <code>Double.longBitsToDouble(0x1L)</code>.
     */
//  public static final double MIN_VALUE = 4.94065645841246544e-324;
//  public static final double MIN_VALUE = 4.9e-324;  // From jdk 1.4.2
    public static final double MIN_VALUE = longBitsToDouble(1L);

    /**
     * The <code>Class</code> instance representing the primitive type
     * <code>double</code>.
     *
     * @since JDK1.1 
     */
    public static final Class	TYPE = Class.getPrimitiveClass("double");

    /**
     * Returns a string representation of the <code>double</code> 
     * argument. All characters mentioned below are ASCII characters.
     * <ul>
     * <li>If the argument is NaN, the result is the string
     *     &quot;<code>NaN</code>&quot;.
     * <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>'&#92;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>'&#92;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> &lt;= <i>m</i> &lt;
     * 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 &lt;= <i>a</i> &lt; 10. The
     * magnitude is then represented as the integer part of <i>a</i>,
     * as a single decimal digit, followed by '<code>.</code>'
     * (<code>'&#92;u002E'</code>), followed by decimal digits
     * representing the fractional part of <i>a</i>, followed by the
     * letter '<code>E</code>' (<code>'&#92;u0045'</code>), followed
     * by a representation of <i>n</i> as a decimal integer, as
     * produced by the method {@link Integer#toString(int)}.
     * </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>double</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>d</i>. Then <i>d</i> must be the <code>double</code> value nearest 
     * to <i>x</i>; or if two <code>double</code> values are equally close 
     * to <i>x</i>, then <i>d</i> must be one of them and the least
     * significant bit of the significand of <i>d</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   d   the <code>double</code> to be converted.
     * @return a string representation of the argument.
     */
    public static String toString(double d) {
	return new FloatingDecimal(d).toJavaFormatString();
    }

    /**
     * Returns a <code>Double</code> object holding the
     * <code>double</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 rule:
     * <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">&sect;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>double</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>Double</code> object representing this
     * <code>double</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.  The two-step
     * sequence of conversions, string to <code>float</code> followed
     * by <code>float</code> to <code>double</code>, is <em>not</em>
     * equivalent to converting a string directly to
     * <code>double</code>. For example, the <code>float</code>
     * literal <code>0.1f</code> is equal to the <code>double</code>
     * value <code>0.10000000149011612</code>; the <code>float</code>
     * literal <code>0.1f</code> represents a different numerical
     * value than the <code>double</code> literal
     * <code>0.1</code>. (The numerical value 0.1 cannot be exactly
     * represented in a binary floating-point number.)
     *
     * @param      s   the string to be parsed.
     * @return     a <code>Double</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 Double valueOf(String s) throws NumberFormatException {
	return new Double(FloatingDecimal.readJavaFormatString(s).doubleValue());
    }

    /**
     * Returns a new <code>double</code> initialized to the value
     * represented by the specified <code>String</code>, as performed
     * by the <code>valueOf</code> method of class
     * <code>Double</code>.
     *
     * @param      s   the string to be parsed.
     * @return the <code>double</code> value represented by the string
     *         argument.
     * @exception NumberFormatException if the string does not contain
     *            a parsable <code>double</code>.
     * @see        java.lang.Double#valueOf(String)
     * @since 1.2
     */
    public static double parseDouble(String s) throws NumberFormatException {
	return FloatingDecimal.readJavaFormatString(s).doubleValue();
    }

    /**
     * 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 value of the argument is NaN;
     *          <code>false</code> otherwise.
     */
    static public boolean isNaN(double 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 value of the argument is positive
     *          infinity or negative infinity; <code>false</code> otherwise.
     */
    static public boolean isInfinite(double v) {
	return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY);
    }

    /**
     * The value of the Double.
     *
     * @serial
     */
    private double value;

    /**
     * Constructs a newly allocated <code>Double</code> object that
     * represents the primitive <code>double</code> argument.
     *
     * @param   value   the value to be represented by the <code>Double</code>.
     */
    public Double(double value) {
	this.value = value;
    }

    /**
     * Constructs a newly allocated <code>Double</code> object that
     * represents the floating-point value of type <code>double</code>
     * represented by the string. The string is converted to a
     * <code>double</code> value as if by the <code>valueOf</code> method.
     *
     * @param      s   a string to be converted to a <code>Double</code>.
     * @exception  NumberFormatException  if the string does not contain a
     *               parsable number.
     * @see        java.lang.Double#valueOf(java.lang.String)
     */
    public Double(String s) throws NumberFormatException {
	// FIXME: this is inefficient
	this(valueOf(s).doubleValue());
    }

    /**
     * Returns <code>true</code> if this <code>Double</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>Double</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>Double</code> object.
     * The primitive <code>double</code> value represented by this
     * object is converted to a string exactly as if by the method
     * <code>toString</code> of one argument.
     *
     * @return  a <code>String</code> representation of this object.
     * @see java.lang.Double#toString(double)
     */
    public String toString() {
	return String.valueOf(value);
    }

    /**
     * Returns the value of this <code>Double</code> as a <code>byte</code> (by
     * casting to a <code>byte</code>).
     *
     * @return  the <code>double</code> value represented by this object
     *          converted to type <code>byte</code>
     * @since JDK1.1 
     */
    public byte byteValue() {
	return (byte)value;
    }

    /**
     * Returns the value of this <code>Double</code> as a
     * <code>short</code> (by casting to a <code>short</code>).