1 /*
  2  * Copyright (c) 1996, 2024, 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 java.lang;
 27 
 28 import jdk.internal.misc.CDS;
 29 import jdk.internal.value.DeserializeConstructor;
 30 import jdk.internal.vm.annotation.IntrinsicCandidate;
 31 import jdk.internal.vm.annotation.Stable;
 32 
 33 import java.lang.constant.Constable;
 34 import java.lang.constant.DynamicConstantDesc;
 35 import java.util.Optional;
 36 
 37 import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST;
 38 import static java.lang.constant.ConstantDescs.CD_byte;

 39 import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
 40 
 41 /**
 42  * The {@code Byte} class is the {@linkplain
 43  * java.lang##wrapperClass wrapper class} for values of the primitive
 44  * type {@code byte}. An object of type {@code Byte} contains a
 45  * single field whose type is {@code byte}.
 46  *
 47  * <p>In addition, this class provides several methods for converting
 48  * a {@code byte} to a {@code String} and a {@code String} to a {@code
 49  * byte}, as well as other constants and methods useful when dealing
 50  * with a {@code byte}.
 51  *
 52  * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
 53  * class; programmers should treat instances that are
 54  * {@linkplain #equals(Object) equal} as interchangeable and should not
 55  * use instances for synchronization, or unpredictable behavior may
 56  * occur. For example, in a future release, synchronization may fail.
 57  *
 58  * @author  Nakul Saraiya
 59  * @author  Joseph D. Darcy
 60  * @see     java.lang.Number
 61  * @since   1.1
 62  */
 63 @jdk.internal.MigratedValueClass
 64 @jdk.internal.ValueBased
 65 public final class Byte extends Number implements Comparable<Byte>, Constable {
 66 
 67     /**
 68      * A constant holding the minimum value a {@code byte} can
 69      * have, -2<sup>7</sup>.
 70      */
 71     public static final byte   MIN_VALUE = -128;
 72 
 73     /**
 74      * A constant holding the maximum value a {@code byte} can
 75      * have, 2<sup>7</sup>-1.
 76      */
 77     public static final byte   MAX_VALUE = 127;
 78 
 79     /**
 80      * The {@code Class} instance representing the primitive type
 81      * {@code byte}.
 82      */
 83     @SuppressWarnings("unchecked")
 84     public static final Class<Byte>     TYPE = (Class<Byte>) Class.getPrimitiveClass("byte");
 85 
 86     /**
 87      * Returns a new {@code String} object representing the
 88      * specified {@code byte}. The radix is assumed to be 10.
 89      *
 90      * @param b the {@code byte} to be converted
 91      * @return the string representation of the specified {@code byte}
 92      * @see java.lang.Integer#toString(int)
 93      */
 94     public static String toString(byte b) {
 95         return Integer.toString(b);
 96     }
 97 
 98     /**
 99      * Returns an {@link Optional} containing the nominal descriptor for this
100      * instance.
101      *
102      * @return an {@link Optional} describing the {@linkplain Byte} instance
103      * @since 15
104      */
105     @Override
106     public Optional<DynamicConstantDesc<Byte>> describeConstable() {
107         return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
108     }
109 
110     private static final class ByteCache {
111         private ByteCache() {}
112 
113         @Stable
114         static final Byte[] cache;
115         static Byte[] archivedCache;
116 
117         static {
118             final int size = -(-128) + 127 + 1;
119 
120             // Load and use the archived cache if it exists
121             CDS.initializeFromArchive(ByteCache.class);
122             if (archivedCache == null || archivedCache.length != size) {
123                 Byte[] c = new Byte[size];
124                 byte value = (byte)-128;
125                 for(int i = 0; i < size; i++) {
126                     c[i] = new Byte(value++);
127                 }
128                 archivedCache = c;
129             }
130             cache = archivedCache;
131         }
132     }
133 
134     /**
135      * Returns a {@code Byte} instance representing the specified
136      * {@code byte} value.
137      * If a new {@code Byte} instance is not required, this method
138      * should generally be used in preference to the constructor
139      * {@link #Byte(byte)}, as this method is likely to yield
140      * significantly better space and time performance since
141      * all byte values are cached.
142      *
143      * @param  b a byte value.
144      * @return a {@code Byte} instance representing {@code b}.
145      * @since  1.5
146      */
147     @IntrinsicCandidate
148     @DeserializeConstructor
149     public static Byte valueOf(byte b) {
150         final int offset = 128;
151         return ByteCache.cache[(int)b + offset];
152     }
153 
154     /**
155      * Parses the string argument as a signed {@code byte} in the
156      * radix specified by the second argument. The characters in the
157      * string must all be digits, of the specified radix (as
158      * determined by whether {@link java.lang.Character#digit(char,
159      * int)} returns a nonnegative value) except that the first
160      * character may be an ASCII minus sign {@code '-'}
161      * ({@code '\u005Cu002D'}) to indicate a negative value or an
162      * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
163      * indicate a positive value.  The resulting {@code byte} value is
164      * returned.
165      *
166      * <p>An exception of type {@code NumberFormatException} is
167      * thrown if any of the following situations occurs:
168      * <ul>
169      * <li> The first argument is {@code null} or is a string of
170      * length zero.
171      *
172      * <li> The radix is either smaller than {@link
173      * java.lang.Character#MIN_RADIX} or larger than {@link
174      * java.lang.Character#MAX_RADIX}.
175      *
176      * <li> Any character of the string is not a digit of the
177      * specified radix, except that the first character may be a minus
178      * sign {@code '-'} ({@code '\u005Cu002D'}) or plus sign
179      * {@code '+'} ({@code '\u005Cu002B'}) provided that the
180      * string is longer than length 1.
181      *
182      * <li> The value represented by the string is not a value of type
183      * {@code byte}.
184      * </ul>
185      *
186      * @param s         the {@code String} containing the
187      *                  {@code byte}
188      *                  representation to be parsed
189      * @param radix     the radix to be used while parsing {@code s}
190      * @return          the {@code byte} value represented by the string
191      *                   argument in the specified radix
192      * @throws          NumberFormatException If the string does
193      *                  not contain a parsable {@code byte}.
194      */
195     public static byte parseByte(String s, int radix)
196         throws NumberFormatException {
197         int i = Integer.parseInt(s, radix);
198         if (i < MIN_VALUE || i > MAX_VALUE)
199             throw new NumberFormatException(
200                 "Value out of range. Value:\"" + s + "\" Radix:" + radix);
201         return (byte)i;
202     }
203 
204     /**
205      * Parses the string argument as a signed decimal {@code
206      * byte}. The characters in the string must all be decimal digits,
207      * except that the first character may be an ASCII minus sign
208      * {@code '-'} ({@code '\u005Cu002D'}) to indicate a negative
209      * value or an ASCII plus sign {@code '+'}
210      * ({@code '\u005Cu002B'}) to indicate a positive value. The
211      * resulting {@code byte} value is returned, exactly as if the
212      * argument and the radix 10 were given as arguments to the {@link
213      * #parseByte(java.lang.String, int)} method.
214      *
215      * @param s         a {@code String} containing the
216      *                  {@code byte} representation to be parsed
217      * @return          the {@code byte} value represented by the
218      *                  argument in decimal
219      * @throws          NumberFormatException if the string does not
220      *                  contain a parsable {@code byte}.
221      */
222     public static byte parseByte(String s) throws NumberFormatException {
223         return parseByte(s, 10);
224     }
225 
226     /**
227      * Returns a {@code Byte} object holding the value
228      * extracted from the specified {@code String} when parsed
229      * with the radix given by the second argument. The first argument
230      * is interpreted as representing a signed {@code byte} in
231      * the radix specified by the second argument, exactly as if the
232      * argument were given to the {@link #parseByte(java.lang.String,
233      * int)} method. The result is a {@code Byte} object that
234      * represents the {@code byte} value specified by the string.
235      *
236      * <p> In other words, this method returns a {@code Byte} object
237      * equal to the value of:
238      *
239      * <blockquote>
240      * {@code Byte.valueOf(Byte.parseByte(s, radix))}
241      * </blockquote>
242      *
243      * @param s         the string to be parsed
244      * @param radix     the radix to be used in interpreting {@code s}
245      * @return          a {@code Byte} object holding the value
246      *                  represented by the string argument in the
247      *                  specified radix.
248      * @throws          NumberFormatException If the {@code String} does
249      *                  not contain a parsable {@code byte}.
250      */
251     public static Byte valueOf(String s, int radix)
252         throws NumberFormatException {
253         return valueOf(parseByte(s, radix));
254     }
255 
256     /**
257      * Returns a {@code Byte} object holding the value
258      * given by the specified {@code String}. The argument is
259      * interpreted as representing a signed decimal {@code byte},
260      * exactly as if the argument were given to the {@link
261      * #parseByte(java.lang.String)} method. The result is a
262      * {@code Byte} object that represents the {@code byte}
263      * value specified by the string.
264      *
265      * <p> In other words, this method returns a {@code Byte} object
266      * equal to the value of:
267      *
268      * <blockquote>
269      * {@code Byte.valueOf(Byte.parseByte(s))}
270      * </blockquote>
271      *
272      * @param s         the string to be parsed
273      * @return          a {@code Byte} object holding the value
274      *                  represented by the string argument
275      * @throws          NumberFormatException If the {@code String} does
276      *                  not contain a parsable {@code byte}.
277      */
278     public static Byte valueOf(String s) throws NumberFormatException {
279         return valueOf(s, 10);
280     }
281 
282     /**
283      * Decodes a {@code String} into a {@code Byte}.
284      * Accepts decimal, hexadecimal, and octal numbers given by
285      * the following grammar:
286      *
287      * <blockquote>
288      * <dl>
289      * <dt><i>DecodableString:</i>
290      * <dd><i>Sign<sub>opt</sub> DecimalNumeral</i>
291      * <dd><i>Sign<sub>opt</sub></i> {@code 0x} <i>HexDigits</i>
292      * <dd><i>Sign<sub>opt</sub></i> {@code 0X} <i>HexDigits</i>
293      * <dd><i>Sign<sub>opt</sub></i> {@code #} <i>HexDigits</i>
294      * <dd><i>Sign<sub>opt</sub></i> {@code 0} <i>OctalDigits</i>
295      *
296      * <dt><i>Sign:</i>
297      * <dd>{@code -}
298      * <dd>{@code +}
299      * </dl>
300      * </blockquote>
301      *
302      * <i>DecimalNumeral</i>, <i>HexDigits</i>, and <i>OctalDigits</i>
303      * are as defined in section {@jls 3.10.1} of
304      * <cite>The Java Language Specification</cite>,
305      * except that underscores are not accepted between digits.
306      *
307      * <p>The sequence of characters following an optional
308      * sign and/or radix specifier ("{@code 0x}", "{@code 0X}",
309      * "{@code #}", or leading zero) is parsed as by the {@code
310      * Byte.parseByte} method with the indicated radix (10, 16, or 8).
311      * This sequence of characters must represent a positive value or
312      * a {@link NumberFormatException} will be thrown.  The result is
313      * negated if first character of the specified {@code String} is
314      * the minus sign.  No whitespace characters are permitted in the
315      * {@code String}.
316      *
317      * @param     nm the {@code String} to decode.
318      * @return   a {@code Byte} object holding the {@code byte}
319      *          value represented by {@code nm}
320      * @throws  NumberFormatException  if the {@code String} does not
321      *            contain a parsable {@code byte}.
322      * @see java.lang.Byte#parseByte(java.lang.String, int)
323      */
324     public static Byte decode(String nm) throws NumberFormatException {
325         int i = Integer.decode(nm);
326         if (i < MIN_VALUE || i > MAX_VALUE)
327             throw new NumberFormatException(
328                     "Value " + i + " out of range from input " + nm);
329         return valueOf((byte)i);
330     }
331 
332     /**
333      * The value of the {@code Byte}.
334      *
335      * @serial
336      */
337     private final byte value;
338 
339     /**
340      * Constructs a newly allocated {@code Byte} object that
341      * represents the specified {@code byte} value.
342      *
343      * @param value     the value to be represented by the
344      *                  {@code Byte}.
345      *
346      * @deprecated
347      * It is rarely appropriate to use this constructor. The static factory
348      * {@link #valueOf(byte)} is generally a better choice, as it is
349      * likely to yield significantly better space and time performance.
350      */
351     @Deprecated(since="9", forRemoval = true)
352     public Byte(byte value) {
353         this.value = value;
354     }
355 
356     /**
357      * Constructs a newly allocated {@code Byte} object that
358      * represents the {@code byte} value indicated by the
359      * {@code String} parameter. The string is converted to a
360      * {@code byte} value in exactly the manner used by the
361      * {@code parseByte} method for radix 10.
362      *
363      * @param s         the {@code String} to be converted to a
364      *                  {@code Byte}
365      * @throws          NumberFormatException if the {@code String}
366      *                  does not contain a parsable {@code byte}.
367      *
368      * @deprecated
369      * It is rarely appropriate to use this constructor.
370      * Use {@link #parseByte(String)} to convert a string to a
371      * {@code byte} primitive, or use {@link #valueOf(String)}
372      * to convert a string to a {@code Byte} object.
373      */
374     @Deprecated(since="9", forRemoval = true)
375     public Byte(String s) throws NumberFormatException {
376         this.value = parseByte(s, 10);
377     }
378 
379     /**
380      * Returns the value of this {@code Byte} as a
381      * {@code byte}.
382      */
383     @IntrinsicCandidate
384     public byte byteValue() {
385         return value;
386     }
387 
388     /**
389      * Returns the value of this {@code Byte} as a {@code short} after
390      * a widening primitive conversion.
391      * @jls 5.1.2 Widening Primitive Conversion
392      */
393     public short shortValue() {
394         return (short)value;
395     }
396 
397     /**
398      * Returns the value of this {@code Byte} as an {@code int} after
399      * a widening primitive conversion.
400      * @jls 5.1.2 Widening Primitive Conversion
401      */
402     public int intValue() {
403         return (int)value;
404     }
405 
406     /**
407      * Returns the value of this {@code Byte} as a {@code long} after
408      * a widening primitive conversion.
409      * @jls 5.1.2 Widening Primitive Conversion
410      */
411     public long longValue() {
412         return (long)value;
413     }
414 
415     /**
416      * Returns the value of this {@code Byte} as a {@code float} after
417      * a widening primitive conversion.
418      * @jls 5.1.2 Widening Primitive Conversion
419      */
420     public float floatValue() {
421         return (float)value;
422     }
423 
424     /**
425      * Returns the value of this {@code Byte} as a {@code double}
426      * after a widening primitive conversion.
427      * @jls 5.1.2 Widening Primitive Conversion
428      */
429     public double doubleValue() {
430         return (double)value;
431     }
432 
433     /**
434      * Returns a {@code String} object representing this
435      * {@code Byte}'s value.  The value is converted to signed
436      * decimal representation and returned as a string, exactly as if
437      * the {@code byte} value were given as an argument to the
438      * {@link java.lang.Byte#toString(byte)} method.
439      *
440      * @return  a string representation of the value of this object in
441      *          base&nbsp;10.
442      */
443     @Override
444     public String toString() {
445         return Integer.toString(value);
446     }
447 
448     /**
449      * Returns a hash code for this {@code Byte}; equal to the result
450      * of invoking {@code intValue()}.
451      *
452      * @return a hash code value for this {@code Byte}
453      */
454     @Override
455     public int hashCode() {
456         return Byte.hashCode(value);
457     }
458 
459     /**
460      * Returns a hash code for a {@code byte} value; compatible with
461      * {@code Byte.hashCode()}.
462      *
463      * @param value the value to hash
464      * @return a hash code value for a {@code byte} value.
465      * @since 1.8
466      */
467     public static int hashCode(byte value) {
468         return (int)value;
469     }
470 
471     /**
472      * Compares this object to the specified object.  The result is
473      * {@code true} if and only if the argument is not
474      * {@code null} and is a {@code Byte} object that
475      * contains the same {@code byte} value as this object.
476      *
477      * @param obj       the object to compare with
478      * @return          {@code true} if the objects are the same;
479      *                  {@code false} otherwise.
480      */
481     public boolean equals(Object obj) {
482         if (obj instanceof Byte) {
483             return value == ((Byte)obj).byteValue();
484         }
485         return false;
486     }
487 
488     /**
489      * Compares two {@code Byte} objects numerically.
490      *
491      * @param   anotherByte   the {@code Byte} to be compared.
492      * @return  the value {@code 0} if this {@code Byte} is
493      *          equal to the argument {@code Byte}; a value less than
494      *          {@code 0} if this {@code Byte} is numerically less
495      *          than the argument {@code Byte}; and a value greater than
496      *           {@code 0} if this {@code Byte} is numerically
497      *           greater than the argument {@code Byte} (signed
498      *           comparison).
499      * @since   1.2
500      */
501     public int compareTo(Byte anotherByte) {
502         return compare(this.value, anotherByte.value);
503     }
504 
505     /**
506      * Compares two {@code byte} values numerically.
507      * The value returned is identical to what would be returned by:
508      * <pre>
509      *    Byte.valueOf(x).compareTo(Byte.valueOf(y))
510      * </pre>
511      *
512      * @param  x the first {@code byte} to compare
513      * @param  y the second {@code byte} to compare
514      * @return the value {@code 0} if {@code x == y};
515      *         a value less than {@code 0} if {@code x < y}; and
516      *         a value greater than {@code 0} if {@code x > y}
517      * @since 1.7
518      */
519     public static int compare(byte x, byte y) {
520         return x - y;
521     }
522 
523     /**
524      * Compares two {@code byte} values numerically treating the values
525      * as unsigned.
526      *
527      * @param  x the first {@code byte} to compare
528      * @param  y the second {@code byte} to compare
529      * @return the value {@code 0} if {@code x == y}; a value less
530      *         than {@code 0} if {@code x < y} as unsigned values; and
531      *         a value greater than {@code 0} if {@code x > y} as
532      *         unsigned values
533      * @since 9
534      */
535     public static int compareUnsigned(byte x, byte y) {
536         return Byte.toUnsignedInt(x) - Byte.toUnsignedInt(y);
537     }
538 
539     /**
540      * Converts the argument to an {@code int} by an unsigned
541      * conversion.  In an unsigned conversion to an {@code int}, the
542      * high-order 24 bits of the {@code int} are zero and the
543      * low-order 8 bits are equal to the bits of the {@code byte} argument.
544      *
545      * Consequently, zero and positive {@code byte} values are mapped
546      * to a numerically equal {@code int} value and negative {@code
547      * byte} values are mapped to an {@code int} value equal to the
548      * input plus 2<sup>8</sup>.
549      *
550      * @param  x the value to convert to an unsigned {@code int}
551      * @return the argument converted to {@code int} by an unsigned
552      *         conversion
553      * @since 1.8
554      */
555     public static int toUnsignedInt(byte x) {
556         return ((int) x) & 0xff;
557     }
558 
559     /**
560      * Converts the argument to a {@code long} by an unsigned
561      * conversion.  In an unsigned conversion to a {@code long}, the
562      * high-order 56 bits of the {@code long} are zero and the
563      * low-order 8 bits are equal to the bits of the {@code byte} argument.
564      *
565      * Consequently, zero and positive {@code byte} values are mapped
566      * to a numerically equal {@code long} value and negative {@code
567      * byte} values are mapped to a {@code long} value equal to the
568      * input plus 2<sup>8</sup>.
569      *
570      * @param  x the value to convert to an unsigned {@code long}
571      * @return the argument converted to {@code long} by an unsigned
572      *         conversion
573      * @since 1.8
574      */
575     public static long toUnsignedLong(byte x) {
576         return ((long) x) & 0xffL;
577     }
578 
579 
580     /**
581      * The number of bits used to represent a {@code byte} value in two's
582      * complement binary form.
583      *
584      * @since 1.5
585      */
586     public static final int SIZE = 8;
587 
588     /**
589      * The number of bytes used to represent a {@code byte} value in two's
590      * complement binary form.
591      *
592      * @since 1.8
593      */
594     public static final int BYTES = SIZE / Byte.SIZE;
595 
596     /** use serialVersionUID from JDK 1.1. for interoperability */
597     @java.io.Serial
598     private static final long serialVersionUID = -7183698231559129828L;
599 }
--- EOF ---