1 /*
2 * Copyright (c) 1996, 2025, 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.vm.annotation.AOTSafeClassInitializer;
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 * @see java.lang.Number
59 * @since 1.1
60 */
61 @jdk.internal.ValueBased
62 public final class Byte extends Number implements Comparable<Byte>, Constable {
63
64 /**
65 * A constant holding the minimum value a {@code byte} can
66 * have, -2<sup>7</sup>.
67 */
68 public static final byte MIN_VALUE = -128;
69
70 /**
71 * A constant holding the maximum value a {@code byte} can
72 * have, 2<sup>7</sup>-1.
73 */
74 public static final byte MAX_VALUE = 127;
75
76 /**
77 * The {@code Class} instance representing the primitive type
78 * {@code byte}.
79 */
80 public static final Class<Byte> TYPE = Class.getPrimitiveClass("byte");
95 * Returns an {@link Optional} containing the nominal descriptor for this
96 * instance.
97 *
98 * @return an {@link Optional} describing the {@linkplain Byte} instance
99 * @since 15
100 */
101 @Override
102 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
103 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
104 }
105
106 @AOTSafeClassInitializer
107 private static final class ByteCache {
108 private ByteCache() {}
109
110 @Stable
111 static final Byte[] cache;
112 static Byte[] archivedCache;
113
114 static {
115 final int size = -(-128) + 127 + 1;
116
117 // Load and use the archived cache if it exists
118 CDS.initializeFromArchive(ByteCache.class);
119 if (archivedCache == null) {
120 Byte[] c = new Byte[size];
121 byte value = (byte)-128;
122 for(int i = 0; i < size; i++) {
123 c[i] = new Byte(value++);
124 }
125 archivedCache = c;
126 }
127 cache = archivedCache;
128 assert cache.length == size;
129 }
130 }
131
132 /**
133 * Returns a {@code Byte} instance representing the specified
134 * {@code byte} value.
135 * If a new {@code Byte} instance is not required, this method
136 * should generally be used in preference to the constructor
137 * {@link #Byte(byte)}, as this method is likely to yield
138 * significantly better space and time performance since
139 * all byte values are cached.
140 *
141 * @param b a byte value.
142 * @return a {@code Byte} instance representing {@code b}.
143 * @since 1.5
144 */
145 @IntrinsicCandidate
146 public static Byte valueOf(byte b) {
147 final int offset = 128;
148 return ByteCache.cache[(int)b + offset];
149 }
150
151 /**
152 * Parses the string argument as a signed {@code byte} in the
153 * radix specified by the second argument. The characters in the
154 * string must all be digits, of the specified radix (as
155 * determined by whether {@link java.lang.Character#digit(char,
156 * int)} returns a nonnegative value) except that the first
157 * character may be an ASCII minus sign {@code '-'}
158 * ({@code '\u005Cu002D'}) to indicate a negative value or an
159 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
160 * indicate a positive value. The resulting {@code byte} value is
161 * returned.
162 *
163 * <p>An exception of type {@code NumberFormatException} is
164 * thrown if any of the following situations occurs:
165 * <ul>
166 * <li> The first argument is {@code null} or is a string of
167 * length zero.
168 *
|
1 /*
2 * Copyright (c) 1996, 2026, 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.misc.PreviewFeatures;
30 import jdk.internal.value.DeserializeConstructor;
31 import jdk.internal.vm.annotation.AOTSafeClassInitializer;
32 import jdk.internal.vm.annotation.IntrinsicCandidate;
33 import jdk.internal.vm.annotation.Stable;
34
35 import java.lang.constant.Constable;
36 import java.lang.constant.DynamicConstantDesc;
37 import java.util.Optional;
38
39 import static java.lang.constant.ConstantDescs.BSM_EXPLICIT_CAST;
40 import static java.lang.constant.ConstantDescs.CD_byte;
41 import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
42
43 /**
44 * The {@code Byte} class is the {@linkplain
45 * java.lang##wrapperClass wrapper class} for values of the primitive
46 * type {@code byte}. An object of type {@code Byte} contains a
47 * single field whose type is {@code byte}.
48 *
49 * <p>In addition, this class provides several methods for converting
50 * a {@code byte} to a {@code String} and a {@code String} to a {@code
51 * byte}, as well as other constants and methods useful when dealing
52 * with a {@code byte}.
53 *
54 * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
55 * class; programmers should treat instances that are {@linkplain #equals(Object) equal}
56 * as interchangeable and should not use instances for synchronization, mutexes, or
57 * with {@linkplain java.lang.ref.Reference object references}.
58 *
59 * <div class="preview-block">
60 * <div class="preview-comment">
61 * When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
62 * Use of value class instances for synchronization, mutexes, or with
63 * {@linkplain java.lang.ref.Reference object references} result in
64 * {@link IdentityException}.
65 * </div>
66 * </div>
67 *
68 * @see java.lang.Number
69 * @since 1.1
70 */
71 @jdk.internal.MigratedValueClass
72 @jdk.internal.ValueBased
73 public final class Byte extends Number implements Comparable<Byte>, Constable {
74
75 /**
76 * A constant holding the minimum value a {@code byte} can
77 * have, -2<sup>7</sup>.
78 */
79 public static final byte MIN_VALUE = -128;
80
81 /**
82 * A constant holding the maximum value a {@code byte} can
83 * have, 2<sup>7</sup>-1.
84 */
85 public static final byte MAX_VALUE = 127;
86
87 /**
88 * The {@code Class} instance representing the primitive type
89 * {@code byte}.
90 */
91 public static final Class<Byte> TYPE = Class.getPrimitiveClass("byte");
106 * Returns an {@link Optional} containing the nominal descriptor for this
107 * instance.
108 *
109 * @return an {@link Optional} describing the {@linkplain Byte} instance
110 * @since 15
111 */
112 @Override
113 public Optional<DynamicConstantDesc<Byte>> describeConstable() {
114 return Optional.of(DynamicConstantDesc.ofNamed(BSM_EXPLICIT_CAST, DEFAULT_NAME, CD_byte, intValue()));
115 }
116
117 @AOTSafeClassInitializer
118 private static final class ByteCache {
119 private ByteCache() {}
120
121 @Stable
122 static final Byte[] cache;
123 static Byte[] archivedCache;
124
125 static {
126 if (!PreviewFeatures.isEnabled()) {
127 final int size = -(-128) + 127 + 1;
128
129 // Load and use the archived cache if it exists
130 CDS.initializeFromArchive(ByteCache.class);
131 if (archivedCache == null) {
132 Byte[] c = new Byte[size];
133 byte value = (byte)-128;
134 for(int i = 0; i < size; i++) {
135 c[i] = new Byte(value++);
136 }
137 archivedCache = c;
138 }
139 cache = archivedCache;
140 assert cache.length == size;
141 } else {
142 cache = null;
143 assert archivedCache == null;
144 }
145 }
146 }
147
148 /**
149 * Returns a {@code Byte} instance representing the specified
150 * {@code byte} value.
151 * <div class="preview-block">
152 * <div class="preview-comment">
153 * <p>
154 * - When preview features are NOT enabled, {@code Byte} is an identity class.
155 * If a new {@code Byte} instance is not required, this method
156 * should generally be used in preference to the constructor
157 * {@link #Byte(byte)}, as this method is likely to yield
158 * significantly better space and time performance since
159 * all byte values are cached.
160 * </p>
161 * <p>
162 * - When preview features are enabled, {@code Byte} is a {@linkplain Class#isValue value class}.
163 * The {@code valueOf} behavior is the same as invoking the constructor,
164 * whether cached or not.
165 * </p>
166 * </div>
167 * </div>
168 *
169 * @param b a byte value.
170 * @return a {@code Byte} instance representing {@code b}.
171 * @since 1.5
172 */
173 @IntrinsicCandidate
174 @DeserializeConstructor
175 public static Byte valueOf(byte b) {
176 if (!PreviewFeatures.isEnabled()) {
177 final int offset = 128;
178 return ByteCache.cache[(int) b + offset];
179 }
180 return new Byte(b);
181 }
182
183 /**
184 * Parses the string argument as a signed {@code byte} in the
185 * radix specified by the second argument. The characters in the
186 * string must all be digits, of the specified radix (as
187 * determined by whether {@link java.lang.Character#digit(char,
188 * int)} returns a nonnegative value) except that the first
189 * character may be an ASCII minus sign {@code '-'}
190 * ({@code '\u005Cu002D'}) to indicate a negative value or an
191 * ASCII plus sign {@code '+'} ({@code '\u005Cu002B'}) to
192 * indicate a positive value. The resulting {@code byte} value is
193 * returned.
194 *
195 * <p>An exception of type {@code NumberFormatException} is
196 * thrown if any of the following situations occurs:
197 * <ul>
198 * <li> The first argument is {@code null} or is a string of
199 * length zero.
200 *
|