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      1 /*
      2  * Copyright (c) 2003, Oracle and/or its affiliates. All rights reserved.
      3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
      4  *
      5  * This code is free software; you can redistribute it and/or modify it
      6  * under the terms of the GNU General Public License version 2 only, as
      7  * published by the Free Software Foundation.  Oracle designates this
      8  * particular file as subject to the "Classpath" exception as provided
      9  * by Oracle in the LICENSE file that accompanied this code.
     10  *
     11  * This code is distributed in the hope that it will be useful, but WITHOUT
     12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
     14  * version 2 for more details (a copy is included in the LICENSE file that
     15  * accompanied this code).
     16  *
     17  * You should have received a copy of the GNU General Public License version
     18  * 2 along with this work; if not, write to the Free Software Foundation,
     19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
     20  *
     21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
     22  * or visit www.oracle.com if you need additional information or have any
     23  * questions.
     24  */
     25 
     26 package sun.misc;
     27 
     28 /**
     29  * This class contains additional constants documenting limits of the
     30  * <code>double</code> type.
     31  *
     32  * @author Joseph D. Darcy
     33  */
     34 
     35 public class DoubleConsts {
     36     /**
     37      * Don't let anyone instantiate this class.
     38      */
     39     private DoubleConsts() {}
     40 
     41     public static final double POSITIVE_INFINITY = java.lang.Double.POSITIVE_INFINITY;
     42     public static final double NEGATIVE_INFINITY = java.lang.Double.NEGATIVE_INFINITY;
     43     public static final double NaN = java.lang.Double.NaN;
     44     public static final double MAX_VALUE = java.lang.Double.MAX_VALUE;
     45     public static final double MIN_VALUE = java.lang.Double.MIN_VALUE;
     46 
     47     /**
     48      * A constant holding the smallest positive normal value of type
     49      * <code>double</code>, 2<sup>-1022</sup>.  It is equal to the
     50      * value returned by
     51      * <code>Double.longBitsToDouble(0x0010000000000000L)</code>.
     52      *
     53      * @since 1.5
     54      */
     55     public static final double  MIN_NORMAL      = 2.2250738585072014E-308;
     56 
     57 
     58     /**
     59      * The number of logical bits in the significand of a
     60      * <code>double</code> number, including the implicit bit.
     61      */
     62     public static final int SIGNIFICAND_WIDTH   = 53;
     63 
     64     /**
     65      * Maximum exponent a finite <code>double</code> number may have.
     66      * It is equal to the value returned by
     67      * <code>Math.ilogb(Double.MAX_VALUE)</code>.
     68      */
     69     public static final int     MAX_EXPONENT    = 1023;
     70 
     71     /**
     72      * Minimum exponent a normalized <code>double</code> number may
     73      * have.  It is equal to the value returned by
     74      * <code>Math.ilogb(Double.MIN_NORMAL)</code>.
     75      */
     76     public static final int     MIN_EXPONENT    = -1022;
     77 
     78     /**
     79      * The exponent the smallest positive <code>double</code>
     80      * subnormal value would have if it could be normalized.  It is
     81      * equal to the value returned by
     82      * <code>FpUtils.ilogb(Double.MIN_VALUE)</code>.
     83      */
     84     public static final int     MIN_SUB_EXPONENT = MIN_EXPONENT -
     85                                                    (SIGNIFICAND_WIDTH - 1);
     86 
     87     /**
     88      * Bias used in representing a <code>double</code> exponent.
     89      */
     90     public static final int     EXP_BIAS        = 1023;
     91 
     92     /**
     93      * Bit mask to isolate the sign bit of a <code>double</code>.
     94      */
     95     public static final long    SIGN_BIT_MASK   = 0x8000000000000000L;
     96 
     97     /**
     98      * Bit mask to isolate the exponent field of a
     99      * <code>double</code>.
    100      */
    101     public static final long    EXP_BIT_MASK    = 0x7FF0000000000000L;
    102 
    103     /**
    104      * Bit mask to isolate the significand field of a
    105      * <code>double</code>.
    106      */
    107     public static final long    SIGNIF_BIT_MASK = 0x000FFFFFFFFFFFFFL;
    108 
    109     static {
    110         // verify bit masks cover all bit positions and that the bit
    111         // masks are non-overlapping
    112         assert(((SIGN_BIT_MASK | EXP_BIT_MASK | SIGNIF_BIT_MASK) == ~0L) &&
    113                (((SIGN_BIT_MASK & EXP_BIT_MASK) == 0L) &&
    114                 ((SIGN_BIT_MASK & SIGNIF_BIT_MASK) == 0L) &&
    115                 ((EXP_BIT_MASK & SIGNIF_BIT_MASK) == 0L)));
    116     }
    117 }
    118