Java tutorial
/* * Copyright (c) 1994, 2019, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code 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. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code 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 in the LICENSE file that * accompanied this code). * * 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.lang; import java.lang.invoke.MethodHandles; import java.lang.constant.Constable; import java.lang.constant.ConstantDesc; import java.util.Optional; import jdk.internal.math.FloatingDecimal; import jdk.internal.math.DoubleConsts; import jdk.internal.HotSpotIntrinsicCandidate; /** * The {@code Double} class wraps a value of the primitive type * {@code double} in an object. An object of type * {@code Double} contains a single field whose type is * {@code double}. * * <p>In addition, this class provides several methods for converting a * {@code double} to a {@code String} and a * {@code String} to a {@code double}, as well as other * constants and methods useful when dealing with a * {@code double}. * * @author Lee Boynton * @author Arthur van Hoff * @author Joseph D. Darcy * @since 1.0 */ public final class Double extends Number implements Comparable<Double>, Constable, ConstantDesc { /** * A constant holding the positive infinity of type * {@code double}. It is equal to the value returned by * {@code Double.longBitsToDouble(0x7ff0000000000000L)}. */ public static final double POSITIVE_INFINITY = 1.0 / 0.0; /** * A constant holding the negative infinity of type * {@code double}. It is equal to the value returned by * {@code Double.longBitsToDouble(0xfff0000000000000L)}. */ public static final double NEGATIVE_INFINITY = -1.0 / 0.0; /** * A constant holding a Not-a-Number (NaN) value of type * {@code double}. It is equivalent to the value returned by * {@code Double.longBitsToDouble(0x7ff8000000000000L)}. */ public static final double NaN = 0.0d / 0.0; /** * A constant holding the largest positive finite value of type * {@code double}, * (2-2<sup>-52</sup>)·2<sup>1023</sup>. It is equal to * the hexadecimal floating-point literal * {@code 0x1.fffffffffffffP+1023} and also equal to * {@code Double.longBitsToDouble(0x7fefffffffffffffL)}. */ public static final double MAX_VALUE = 0x1.fffffffffffffP+1023; // 1.7976931348623157e+308 /** * A constant holding the smallest positive normal value of type * {@code double}, 2<sup>-1022</sup>. It is equal to the * hexadecimal floating-point literal {@code 0x1.0p-1022} and also * equal to {@code Double.longBitsToDouble(0x0010000000000000L)}. * * @since 1.6 */ public static final double MIN_NORMAL = 0x1.0p-1022; // 2.2250738585072014E-308 /** * A constant holding the smallest positive nonzero value of type * {@code double}, 2<sup>-1074</sup>. It is equal to the * hexadecimal floating-point literal * {@code 0x0.0000000000001P-1022} and also equal to * {@code Double.longBitsToDouble(0x1L)}. */ public static final double MIN_VALUE = 0x0.0000000000001P-1022; // 4.9e-324 /** * Maximum exponent a finite {@code double} variable may have. * It is equal to the value returned by * {@code Math.getExponent(Double.MAX_VALUE)}. * * @since 1.6 */ public static final int MAX_EXPONENT = 1023; /** * Minimum exponent a normalized {@code double} variable may * have. It is equal to the value returned by * {@code Math.getExponent(Double.MIN_NORMAL)}. * * @since 1.6 */ public static final int MIN_EXPONENT = -1022; /** * The number of bits used to represent a {@code double} value. * * @since 1.5 */ public static final int SIZE = 64; /** * The number of bytes used to represent a {@code double} value. * * @since 1.8 */ public static final int BYTES = SIZE / Byte.SIZE; /** * The {@code Class} instance representing the primitive type * {@code double}. * * @since 1.1 */ @SuppressWarnings("unchecked") public static final Class<Double> TYPE = (Class<Double>) Class.getPrimitiveClass("double"); /** * Returns a string representation of the {@code double} * argument. All characters mentioned below are ASCII characters. * <ul> * <li>If the argument is NaN, the result is the string * "{@code NaN}". * <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 '\u005Cu002D'}); 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"}; thus, positive infinity produces the result * {@code "Infinity"} and negative infinity produces the result * {@code "-Infinity"}. * * <li>If <i>m</i> is zero, it is represented by the characters * {@code "0.0"}; thus, negative zero produces the result * {@code "-0.0"} and positive zero produces the result * {@code "0.0"}. * * <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 '\u005Cu002E'}), 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> {@literal <} * 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> {@literal <} 10. The * magnitude is then represented as the integer part of <i>a</i>, * as a single decimal digit, followed by '{@code .}' * ({@code '\u005Cu002E'}), followed by decimal digits * representing the fractional part of <i>a</i>, followed by the * letter '{@code E}' ({@code '\u005Cu0045'}), 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}. 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} value nearest * to <i>x</i>; or if two {@code double} 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}. * * <p>To create localized string representations of a floating-point * value, use subclasses of {@link java.text.NumberFormat}. * * @param d the {@code double} to be converted. * @return a string representation of the argument. */ public static String toString(double d) { return FloatingDecimal.toJavaFormatString(d); } /** * Returns a hexadecimal string representation of the * {@code double} argument. All characters mentioned below * are ASCII characters. * * <ul> * <li>If the argument is NaN, the result is the string * "{@code NaN}". * <li>Otherwise, the result is a string that represents the sign * and magnitude of the argument. If the sign is negative, the * first character of the result is '{@code -}' * ({@code '\u005Cu002D'}); 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 string * {@code "Infinity"}; thus, positive infinity produces the * result {@code "Infinity"} and negative infinity produces * the result {@code "-Infinity"}. * * <li>If <i>m</i> is zero, it is represented by the string * {@code "0x0.0p0"}; thus, negative zero produces the result * {@code "-0x0.0p0"} and positive zero produces the result * {@code "0x0.0p0"}. * * <li>If <i>m</i> is a {@code double} value with a * normalized representation, substrings are used to represent the * significand and exponent fields. The significand is * represented by the characters {@code "0x1."} * followed by a lowercase hexadecimal representation of the rest * of the significand as a fraction. Trailing zeros in the * hexadecimal representation are removed unless all the digits * are zero, in which case a single zero is used. Next, the * exponent is represented by {@code "p"} followed * by a decimal string of the unbiased exponent as if produced by * a call to {@link Integer#toString(int) Integer.toString} on the * exponent value. * * <li>If <i>m</i> is a {@code double} value with a subnormal * representation, the significand is represented by the * characters {@code "0x0."} followed by a * hexadecimal representation of the rest of the significand as a * fraction. Trailing zeros in the hexadecimal representation are * removed. Next, the exponent is represented by * {@code "p-1022"}. Note that there must be at * least one nonzero digit in a subnormal significand. * * </ul> * * </ul> * * <table class="striped"> * <caption>Examples</caption> * <thead> * <tr><th scope="col">Floating-point Value</th><th scope="col">Hexadecimal String</th> * </thead> * <tbody style="text-align:right"> * <tr><th scope="row">{@code 1.0}</th> <td>{@code 0x1.0p0}</td> * <tr><th scope="row">{@code -1.0}</th> <td>{@code -0x1.0p0}</td> * <tr><th scope="row">{@code 2.0}</th> <td>{@code 0x1.0p1}</td> * <tr><th scope="row">{@code 3.0}</th> <td>{@code 0x1.8p1}</td> * <tr><th scope="row">{@code 0.5}</th> <td>{@code 0x1.0p-1}</td> * <tr><th scope="row">{@code 0.25}</th> <td>{@code 0x1.0p-2}</td> * <tr><th scope="row">{@code Double.MAX_VALUE}</th> * <td>{@code 0x1.fffffffffffffp1023}</td> * <tr><th scope="row">{@code Minimum Normal Value}</th> * <td>{@code 0x1.0p-1022}</td> * <tr><th scope="row">{@code Maximum Subnormal Value}</th> * <td>{@code 0x0.fffffffffffffp-1022}</td> * <tr><th scope="row">{@code Double.MIN_VALUE}</th> * <td>{@code 0x0.0000000000001p-1022}</td> * </tbody> * </table> * @param d the {@code double} to be converted. * @return a hex string representation of the argument. * @since 1.5 * @author Joseph D. Darcy */ public static String toHexString(double d) { /* * Modeled after the "a" conversion specifier in C99, section * 7.19.6.1; however, the output of this method is more * tightly specified. */ if (!isFinite(d)) // For infinity and NaN, use the decimal output. return Double.toString(d); else { // Initialized to maximum size of output. StringBuilder answer = new StringBuilder(24); if (Math.copySign(1.0, d) == -1.0) // value is negative, answer.append("-"); // so append sign info answer.append("0x"); d = Math.abs(d); if (d == 0.0) { answer.append("0.0p0"); } else { boolean subnormal = (d < Double.MIN_NORMAL); // Isolate significand bits and OR in a high-order bit // so that the string representation has a known // length. long signifBits = (Double.doubleToLongBits(d) & DoubleConsts.SIGNIF_BIT_MASK) | 0x1000000000000000L; // Subnormal values have a 0 implicit bit; normal // values have a 1 implicit bit. answer.append(subnormal ? "0." : "1."); // Isolate the low-order 13 digits of the hex // representation. If all the digits are zero, // replace with a single 0; otherwise, remove all // trailing zeros. String signif = Long.toHexString(signifBits).substring(3, 16); answer.append(signif.equals("0000000000000") ? // 13 zeros "0" : signif.replaceFirst("0{1,12}$", "")); answer.append('p'); // If the value is subnormal, use the E_min exponent // value for double; otherwise, extract and report d's // exponent (the representation of a subnormal uses // E_min -1). answer.append(subnormal ? Double.MIN_EXPONENT : Math.getExponent(d)); } return answer.toString(); } } /** * Returns a {@code Double} object holding the * {@code double} value represented by the argument string * {@code s}. * * <p>If {@code s} is {@code null}, then a * {@code NullPointerException} is thrown. * * <p>Leading and trailing whitespace characters in {@code s} * are ignored. Whitespace is removed as if by the {@link * String#trim} method; that is, both ASCII space and control * characters are removed. The rest of {@code s} should * constitute a <i>FloatValue</i> as described by the lexical * syntax rules: * * <blockquote> * <dl> * <dt><i>FloatValue:</i> * <dd><i>Sign<sub>opt</sub></i> {@code NaN} * <dd><i>Sign<sub>opt</sub></i> {@code Infinity} * <dd><i>Sign<sub>opt</sub> FloatingPointLiteral</i> * <dd><i>Sign<sub>opt</sub> HexFloatingPointLiteral</i> * <dd><i>SignedInteger</i> * </dl> * * <dl> * <dt><i>HexFloatingPointLiteral</i>: * <dd> <i>HexSignificand BinaryExponent FloatTypeSuffix<sub>opt</sub></i> * </dl> * * <dl> * <dt><i>HexSignificand:</i> * <dd><i>HexNumeral</i> * <dd><i>HexNumeral</i> {@code .} * <dd>{@code 0x} <i>HexDigits<sub>opt</sub> * </i>{@code .}<i> HexDigits</i> * <dd>{@code 0X}<i> HexDigits<sub>opt</sub> * </i>{@code .} <i>HexDigits</i> * </dl> * * <dl> * <dt><i>BinaryExponent:</i> * <dd><i>BinaryExponentIndicator SignedInteger</i> * </dl> * * <dl> * <dt><i>BinaryExponentIndicator:</i> * <dd>{@code p} * <dd>{@code P} * </dl> * * </blockquote> * * where <i>Sign</i>, <i>FloatingPointLiteral</i>, * <i>HexNumeral</i>, <i>HexDigits</i>, <i>SignedInteger</i> and * <i>FloatTypeSuffix</i> are as defined in the lexical structure * sections of * <cite>The Java™ Language Specification</cite>, * except that underscores are not accepted between digits. * If {@code s} does not have the form of * a <i>FloatValue</i>, then a {@code NumberFormatException} * is thrown. Otherwise, {@code s} is regarded as * representing an exact decimal value in the usual * "computerized scientific notation" or as an exact * hexadecimal value; this exact numerical value is then * conceptually converted to an "infinitely precise" * binary value that is then rounded to type {@code double} * by the usual round-to-nearest rule of IEEE 754 floating-point * arithmetic, which includes preserving the sign of a zero * value. * * Note that the round-to-nearest rule also implies overflow and * underflow behaviour; if the exact value of {@code s} is large * enough in magnitude (greater than or equal to ({@link * #MAX_VALUE} + {@link Math#ulp(double) ulp(MAX_VALUE)}/2), * rounding to {@code double} will result in an infinity and if the * exact value of {@code s} is small enough in magnitude (less * than or equal to {@link #MIN_VALUE}/2), rounding to float will * result in a zero. * * Finally, after rounding a {@code Double} object representing * this {@code double} 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} is a {@code float} value; * {@code 1.0d} is a {@code double} 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} followed * by {@code float} to {@code double}, is <em>not</em> * equivalent to converting a string directly to * {@code double}. For example, the {@code float} * literal {@code 0.1f} is equal to the {@code double} * value {@code 0.10000000149011612}; the {@code float} * literal {@code 0.1f} represents a different numerical * value than the {@code double} literal * {@code 0.1}. (The numerical value 0.1 cannot be exactly * represented in a binary floating-point number.) * * <p>To avoid calling this method on an invalid string and having * a {@code NumberFormatException} be thrown, the regular * expression below can be used to screen the input string: * * <pre>{@code * final String Digits = "(\\p{Digit}+)"; * final String HexDigits = "(\\p{XDigit}+)"; * // an exponent is 'e' or 'E' followed by an optionally * // signed decimal integer. * final String Exp = "[eE][+-]?"+Digits; * final String fpRegex = * ("[\\x00-\\x20]*"+ // Optional leading "whitespace" * "[+-]?(" + // Optional sign character * "NaN|" + // "NaN" string * "Infinity|" + // "Infinity" string * * // A decimal floating-point string representing a finite positive * // number without a leading sign has at most five basic pieces: * // Digits . Digits ExponentPart FloatTypeSuffix * // * // Since this method allows integer-only strings as input * // in addition to strings of floating-point literals, the * // two sub-patterns below are simplifications of the grammar * // productions from section 3.10.2 of * // The Java Language Specification. * * // Digits ._opt Digits_opt ExponentPart_opt FloatTypeSuffix_opt * "((("+Digits+"(\\.)?("+Digits+"?)("+Exp+")?)|"+ * * // . Digits ExponentPart_opt FloatTypeSuffix_opt * "(\\.("+Digits+")("+Exp+")?)|"+ * * // Hexadecimal strings * "((" + * // 0[xX] HexDigits ._opt BinaryExponent FloatTypeSuffix_opt * "(0[xX]" + HexDigits + "(\\.)?)|" + * * // 0[xX] HexDigits_opt . HexDigits BinaryExponent FloatTypeSuffix_opt * "(0[xX]" + HexDigits + "?(\\.)" + HexDigits + ")" + * * ")[pP][+-]?" + Digits + "))" + * "[fFdD]?))" + * "[\\x00-\\x20]*");// Optional trailing "whitespace" * * if (Pattern.matches(fpRegex, myString)) * Double.valueOf(myString); // Will not throw NumberFormatException * else { * // Perform suitable alternative action * } * }</pre> * * @param s the string to be parsed. * @return a {@code Double} object holding the value * represented by the {@code String} argument. * @throws NumberFormatException if the string does not contain a * parsable number. */ public static Double valueOf(String s) throws NumberFormatException { return new Double(parseDouble(s)); } /** * Returns a {@code Double} instance representing the specified * {@code double} value. * If a new {@code Double} instance is not required, this method * should generally be used in preference to the constructor * {@link #Double(double)}, as this method is likely to yield * significantly better space and time performance by caching * frequently requested values. * * @param d a double value. * @return a {@code Double} instance representing {@code d}. * @since 1.5 */ @HotSpotIntrinsicCandidate public static Double valueOf(double d) { return new Double(d); } /** * Returns a new {@code double} initialized to the value * represented by the specified {@code String}, as performed * by the {@code valueOf} method of class * {@code Double}. * * @param s the string to be parsed. * @return the {@code double} value represented by the string * argument. * @throws NullPointerException if the string is null * @throws NumberFormatException if the string does not contain * a parsable {@code double}. * @see java.lang.Double#valueOf(String) * @since 1.2 */ public static double parseDouble(String s) throws NumberFormatException { return FloatingDecimal.parseDouble(s); } /** * Returns {@code true} if the specified number is a * Not-a-Number (NaN) value, {@code false} otherwise. * * @param v the value to be tested. * @return {@code true} if the value of the argument is NaN; * {@code false} otherwise. */ public static boolean isNaN(double v) { return (v != v); } /** * Returns {@code true} if the specified number is infinitely * large in magnitude, {@code false} otherwise. * * @param v the value to be tested. * @return {@code true} if the value of the argument is positive * infinity or negative infinity; {@code false} otherwise. */ public static boolean isInfinite(double v) { return (v == POSITIVE_INFINITY) || (v == NEGATIVE_INFINITY); } /** * Returns {@code true} if the argument is a finite floating-point * value; returns {@code false} otherwise (for NaN and infinity * arguments). * * @param d the {@code double} value to be tested * @return {@code true} if the argument is a finite * floating-point value, {@code false} otherwise. * @since 1.8 */ public static boolean isFinite(double d) { return Math.abs(d) <= Double.MAX_VALUE; } /** * The value of the Double. * * @serial */ private final double value; /** * Constructs a newly allocated {@code Double} object that * represents the primitive {@code double} argument. * * @param value the value to be represented by the {@code Double}. * * @deprecated * It is rarely appropriate to use this constructor. The static factory * {@link #valueOf(double)} is generally a better choice, as it is * likely to yield significantly better space and time performance. */ @Deprecated(since = "9") public Double(double value) { this.value = value; } /** * Constructs a newly allocated {@code Double} object that * represents the floating-point value of type {@code double} * represented by the string. The string is converted to a * {@code double} value as if by the {@code valueOf} method. * * @param s a string to be converted to a {@code Double}. * @throws NumberFormatException if the string does not contain a * parsable number. * * @deprecated * It is rarely appropriate to use this constructor. * Use {@link #parseDouble(String)} to convert a string to a * {@code double} primitive, or use {@link #valueOf(String)} * to convert a string to a {@code Double} object. */ @Deprecated(since = "9") public Double(String s) throws NumberFormatException { value = parseDouble(s); } /** * Returns {@code true} if this {@code Double} value is * a Not-a-Number (NaN), {@code false} otherwise. * * @return {@code true} if the value represented by this object is * NaN; {@code false} otherwise. */ public boolean isNaN() { return isNaN(value); } /** * Returns {@code true} if this {@code Double} value is * infinitely large in magnitude, {@code false} otherwise. * * @return {@code true} if the value represented by this object is * positive infinity or negative infinity; * {@code false} otherwise. */ public boolean isInfinite() { return isInfinite(value); } /** * Returns a string representation of this {@code Double} object. * The primitive {@code double} value represented by this * object is converted to a string exactly as if by the method * {@code toString} of one argument. * * @return a {@code String} representation of this object. * @see java.lang.Double#toString(double) */ public String toString() { return toString(value); } /** * Returns the value of this {@code Double} as a {@code byte} * after a narrowing primitive conversion. * * @return the {@code double} value represented by this object * converted to type {@code byte} * @jls 5.1.3 Narrowing Primitive Conversion * @since 1.1 */ public byte byteValue() { return (byte) value; } /** * Returns the value of this {@code Double} as a {@code short} * after a narrowing primitive conversion. * * @return the {@code double} value represented by this object * converted to type {@code short} * @jls 5.1.3 Narrowing Primitive Conversion * @since 1.1 */ public short shortValue() { return (short) value; } /** * Returns the value of this {@code Double} as an {@code int} * after a narrowing primitive conversion. * @jls 5.1.3 Narrowing Primitive Conversion * * @return the {@code double} value represented by this object * converted to type {@code int} */ public int intValue() { return (int) value; } /** * Returns the value of this {@code Double} as a {@code long} * after a narrowing primitive conversion. * * @return the {@code double} value represented by this object * converted to type {@code long} * @jls 5.1.3 Narrowing Primitive Conversion */ public long longValue() { return (long) value; } /** * Returns the value of this {@code Double} as a {@code float} * after a narrowing primitive conversion. * * @return the {@code double} value represented by this object * converted to type {@code float} * @jls 5.1.3 Narrowing Primitive Conversion * @since 1.0 */ public float floatValue() { return (float) value; } /** * Returns the {@code double} value of this {@code Double} object. * * @return the {@code double} value represented by this object */ @HotSpotIntrinsicCandidate public double doubleValue() { return value; } /** * Returns a hash code for this {@code Double} object. The * result is the exclusive OR of the two halves of the * {@code long} integer bit representation, exactly as * produced by the method {@link #doubleToLongBits(double)}, of * the primitive {@code double} value represented by this * {@code Double} object. That is, the hash code is the value * of the expression: * * <blockquote> * {@code (int)(v^(v>>>32))} * </blockquote> * * where {@code v} is defined by: * * <blockquote> * {@code long v = Double.doubleToLongBits(this.doubleValue());} * </blockquote> * * @return a {@code hash code} value for this object. */ @Override public int hashCode() { return Double.hashCode(value); } /** * Returns a hash code for a {@code double} value; compatible with * {@code Double.hashCode()}. * * @param value the value to hash * @return a hash code value for a {@code double} value. * @since 1.8 */ public static int hashCode(double value) { long bits = doubleToLongBits(value); return (int) (bits ^ (bits >>> 32)); } /** * Compares this object against the specified object. The result * is {@code true} if and only if the argument is not * {@code null} and is a {@code Double} object that * represents a {@code double} that has the same value as the * {@code double} represented by this object. For this * purpose, two {@code double} values are considered to be * the same if and only if the method {@link * #doubleToLongBits(double)} returns the identical * {@code long} value when applied to each. * * <p>Note that in most cases, for two instances of class * {@code Double}, {@code d1} and {@code d2}, the * value of {@code d1.equals(d2)} is {@code true} if and * only if * * <blockquote> * {@code d1.doubleValue() == d2.doubleValue()} * </blockquote> * * <p>also has the value {@code true}. However, there are two * exceptions: * <ul> * <li>If {@code d1} and {@code d2} both represent * {@code Double.NaN}, then the {@code equals} method * returns {@code true}, even though * {@code Double.NaN==Double.NaN} has the value * {@code false}. * <li>If {@code d1} represents {@code +0.0} while * {@code d2} represents {@code -0.0}, or vice versa, * the {@code equal} test has the value {@code false}, * even though {@code +0.0==-0.0} has the value {@code true}. * </ul> * This definition allows hash tables to operate properly. * @param obj the object to compare with. * @return {@code true} if the objects are the same; * {@code false} otherwise. * @see java.lang.Double#doubleToLongBits(double) */ public boolean equals(Object obj) { return (obj instanceof Double) && (doubleToLongBits(((Double) obj).value) == doubleToLongBits(value)); } /** * Returns a representation of the specified floating-point value * according to the IEEE 754 floating-point "double * format" bit layout. * * <p>Bit 63 (the bit that is selected by the mask * {@code 0x8000000000000000L}) represents the sign of the * floating-point number. Bits * 62-52 (the bits that are selected by the mask * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0 * (the bits that are selected by the mask * {@code 0x000fffffffffffffL}) represent the significand * (sometimes called the mantissa) of the floating-point number. * * <p>If the argument is positive infinity, the result is * {@code 0x7ff0000000000000L}. * * <p>If the argument is negative infinity, the result is * {@code 0xfff0000000000000L}. * * <p>If the argument is NaN, the result is * {@code 0x7ff8000000000000L}. * * <p>In all cases, the result is a {@code long} integer that, when * given to the {@link #longBitsToDouble(long)} method, will produce a * floating-point value the same as the argument to * {@code doubleToLongBits} (except all NaN values are * collapsed to a single "canonical" NaN value). * * @param value a {@code double} precision floating-point number. * @return the bits that represent the floating-point number. */ @HotSpotIntrinsicCandidate public static long doubleToLongBits(double value) { if (!isNaN(value)) { return doubleToRawLongBits(value); } return 0x7ff8000000000000L; } /** * Returns a representation of the specified floating-point value * according to the IEEE 754 floating-point "double * format" bit layout, preserving Not-a-Number (NaN) values. * * <p>Bit 63 (the bit that is selected by the mask * {@code 0x8000000000000000L}) represents the sign of the * floating-point number. Bits * 62-52 (the bits that are selected by the mask * {@code 0x7ff0000000000000L}) represent the exponent. Bits 51-0 * (the bits that are selected by the mask * {@code 0x000fffffffffffffL}) represent the significand * (sometimes called the mantissa) of the floating-point number. * * <p>If the argument is positive infinity, the result is * {@code 0x7ff0000000000000L}. * * <p>If the argument is negative infinity, the result is * {@code 0xfff0000000000000L}. * * <p>If the argument is NaN, the result is the {@code long} * integer representing the actual NaN value. Unlike the * {@code doubleToLongBits} method, * {@code doubleToRawLongBits} does not collapse all the bit * patterns encoding a NaN to a single "canonical" NaN * value. * * <p>In all cases, the result is a {@code long} integer that, * when given to the {@link #longBitsToDouble(long)} method, will * produce a floating-point value the same as the argument to * {@code doubleToRawLongBits}. * * @param value a {@code double} precision floating-point number. * @return the bits that represent the floating-point number. * @since 1.3 */ @HotSpotIntrinsicCandidate public static native long doubleToRawLongBits(double value); /** * Returns the {@code double} value corresponding to a given * bit representation. * The argument is considered to be a representation of a * floating-point value according to the IEEE 754 floating-point * "double format" bit layout. * * <p>If the argument is {@code 0x7ff0000000000000L}, the result * is positive infinity. * * <p>If the argument is {@code 0xfff0000000000000L}, the result * is negative infinity. * * <p>If the argument is any value in the range * {@code 0x7ff0000000000001L} through * {@code 0x7fffffffffffffffL} or in the range * {@code 0xfff0000000000001L} through * {@code 0xffffffffffffffffL}, 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 Double.doubleToRawLongBits} 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>{@code * int s = ((bits >> 63) == 0) ? 1 : -1; * int e = (int)((bits >> 52) & 0x7ffL); * long m = (e == 0) ? * (bits & 0xfffffffffffffL) << 1 : * (bits & 0xfffffffffffffL) | 0x10000000000000L; * }</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>-1075</sup>. * * <p>Note that this method may not be able to return a * {@code double} NaN with exactly same bit pattern as the * {@code long} 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 longBitsToDouble} * may not be able to return a {@code double} with a * signaling NaN bit pattern. Consequently, for some * {@code long} values, * {@code doubleToRawLongBits(longBitsToDouble(start))} may * <i>not</i> equal {@code start}. 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 any {@code long} integer. * @return the {@code double} floating-point value with the same * bit pattern. */ @HotSpotIntrinsicCandidate public static native double longBitsToDouble(long bits); /** * Compares two {@code Double} 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 <, <=, ==, >=, >}) * when applied to primitive {@code double} values: * <ul><li> * {@code Double.NaN} is considered by this method * to be equal to itself and greater than all other * {@code double} values (including * {@code Double.POSITIVE_INFINITY}). * <li> * {@code 0.0d} is considered by this method to be greater * than {@code -0.0d}. * </ul> * This ensures that the <i>natural ordering</i> of * {@code Double} objects imposed by this method is <i>consistent * with equals</i>. * * @param anotherDouble the {@code Double} to be compared. * @return the value {@code 0} if {@code anotherDouble} is * numerically equal to this {@code Double}; a value * less than {@code 0} if this {@code Double} * is numerically less than {@code anotherDouble}; * and a value greater than {@code 0} if this * {@code Double} is numerically greater than * {@code anotherDouble}. * * @since 1.2 */ public int compareTo(Double anotherDouble) { return Double.compare(value, anotherDouble.value); } /** * Compares the two specified {@code double} 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 Double(d1).compareTo(new Double(d2)) * </pre> * * @param d1 the first {@code double} to compare * @param d2 the second {@code double} to compare * @return the value {@code 0} if {@code d1} is * numerically equal to {@code d2}; a value less than * {@code 0} if {@code d1} is numerically less than * {@code d2}; and a value greater than {@code 0} * if {@code d1} is numerically greater than * {@code d2}. * @since 1.4 */ public static int compare(double d1, double d2) { if (d1 < d2) return -1; // Neither val is NaN, thisVal is smaller if (d1 > d2) return 1; // Neither val is NaN, thisVal is larger // Cannot use doubleToRawLongBits because of possibility of NaNs. long thisBits = Double.doubleToLongBits(d1); long anotherBits = Double.doubleToLongBits(d2); 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) } /** * Adds two {@code double} values together as per the + operator. * * @param a the first operand * @param b the second operand * @return the sum of {@code a} and {@code b} * @jls 4.2.4 Floating-Point Operations * @see java.util.function.BinaryOperator * @since 1.8 */ public static double sum(double a, double b) { return a + b; } /** * Returns the greater of two {@code double} values * as if by calling {@link Math#max(double, double) Math.max}. * * @param a the first operand * @param b the second operand * @return the greater of {@code a} and {@code b} * @see java.util.function.BinaryOperator * @since 1.8 */ public static double max(double a, double b) { return Math.max(a, b); } /** * Returns the smaller of two {@code double} values * as if by calling {@link Math#min(double, double) Math.min}. * * @param a the first operand * @param b the second operand * @return the smaller of {@code a} and {@code b}. * @see java.util.function.BinaryOperator * @since 1.8 */ public static double min(double a, double b) { return Math.min(a, b); } /** * Returns an {@link Optional} containing the nominal descriptor for this * instance, which is the instance itself. * * @return an {@link Optional} describing the {@linkplain Double} instance * @since 12 */ @Override public Optional<Double> describeConstable() { return Optional.of(this); } /** * Resolves this instance as a {@link ConstantDesc}, the result of which is * the instance itself. * * @param lookup ignored * @return the {@linkplain Double} instance * @since 12 */ @Override public Double resolveConstantDesc(MethodHandles.Lookup lookup) { return this; } /** use serialVersionUID from JDK 1.0.2 for interoperability */ private static final long serialVersionUID = -9172774392245257468L; }