1 /*
2 * Copyright (c) 1994, 2021, 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.value.DeserializeConstructor;
29 import jdk.internal.vm.annotation.IntrinsicCandidate;
30
31 import java.lang.constant.Constable;
32 import java.lang.constant.ConstantDescs;
33 import java.lang.constant.DynamicConstantDesc;
34 import java.util.Optional;
35
36 /**
37 * The Boolean class wraps a value of the primitive type
38 * {@code boolean} in an object. An object of type
39 * {@code Boolean} contains a single field whose type is
40 * {@code boolean}.
41 *
42 * <p>In addition, this class provides many methods for
43 * converting a {@code boolean} to a {@code String} and a
44 * {@code String} to a {@code boolean}, as well as other
45 * constants and methods useful when dealing with a
46 * {@code boolean}.
47 *
48 * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
49 * class; programmers should treat instances that are
50 * {@linkplain #equals(Object) equal} as interchangeable and should not
51 * use instances for synchronization, or unpredictable behavior may
52 * occur. For example, in a future release, synchronization may fail.
53 *
54 * @author Arthur van Hoff
55 * @since 1.0
56 */
57 @jdk.internal.MigratedValueClass
58 @jdk.internal.ValueBased
59 public final class Boolean implements java.io.Serializable,
60 Comparable<Boolean>, Constable
61 {
62 /**
63 * The {@code Boolean} object corresponding to the primitive
64 * value {@code true}.
65 */
66 public static final Boolean TRUE = new Boolean(true);
67
68 /**
69 * The {@code Boolean} object corresponding to the primitive
70 * value {@code false}.
71 */
72 public static final Boolean FALSE = new Boolean(false);
73
74 /**
75 * The Class object representing the primitive type boolean.
76 *
77 * @since 1.1
78 */
79 @SuppressWarnings("unchecked")
80 public static final Class<Boolean> TYPE = (Class<Boolean>) Class.getPrimitiveClass("boolean");
81
82 /**
83 * The value of the Boolean.
84 *
85 * @serial
86 */
87 private final boolean value;
88
89 /** use serialVersionUID from JDK 1.0.2 for interoperability */
90 @java.io.Serial
91 private static final long serialVersionUID = -3665804199014368530L;
92
93 /**
94 * Allocates a {@code Boolean} object representing the
95 * {@code value} argument.
96 *
97 * @param value the value of the {@code Boolean}.
98 *
99 * @deprecated
100 * It is rarely appropriate to use this constructor. The static factory
101 * {@link #valueOf(boolean)} is generally a better choice, as it is
102 * likely to yield significantly better space and time performance.
103 * Also consider using the final fields {@link #TRUE} and {@link #FALSE}
104 * if possible.
105 */
106 @Deprecated(since="9", forRemoval = true)
107 public Boolean(boolean value) {
108 this.value = value;
109 }
110
111 /**
112 * Allocates a {@code Boolean} object representing the value
113 * {@code true} if the string argument is not {@code null}
114 * and is equal, ignoring case, to the string {@code "true"}.
115 * Otherwise, allocates a {@code Boolean} object representing the
116 * value {@code false}.
117 *
118 * @param s the string to be converted to a {@code Boolean}.
119 *
120 * @deprecated
121 * It is rarely appropriate to use this constructor.
122 * Use {@link #parseBoolean(String)} to convert a string to a
123 * {@code boolean} primitive, or use {@link #valueOf(String)}
124 * to convert a string to a {@code Boolean} object.
125 */
126 @Deprecated(since="9", forRemoval = true)
127 public Boolean(String s) {
128 this(parseBoolean(s));
129 }
130
131 /**
132 * Parses the string argument as a boolean. The {@code boolean}
133 * returned represents the value {@code true} if the string argument
134 * is not {@code null} and is equal, ignoring case, to the string
135 * {@code "true"}.
136 * Otherwise, a false value is returned, including for a null
137 * argument.<p>
138 * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>
139 * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.
140 *
141 * @param s the {@code String} containing the boolean
142 * representation to be parsed
143 * @return the boolean represented by the string argument
144 * @since 1.5
145 */
146 public static boolean parseBoolean(String s) {
147 return "true".equalsIgnoreCase(s);
148 }
149
150 /**
151 * Returns the value of this {@code Boolean} object as a boolean
152 * primitive.
153 *
154 * @return the primitive {@code boolean} value of this object.
155 */
156 @IntrinsicCandidate
157 public boolean booleanValue() {
158 return value;
159 }
160
161 /**
162 * Returns a {@code Boolean} instance representing the specified
163 * {@code boolean} value. If the specified {@code boolean} value
164 * is {@code true}, this method returns {@code Boolean.TRUE};
165 * if it is {@code false}, this method returns {@code Boolean.FALSE}.
166 * If a new {@code Boolean} instance is not required, this method
167 * should generally be used in preference to the constructor
168 * {@link #Boolean(boolean)}, as this method is likely to yield
169 * significantly better space and time performance.
170 *
171 * @param b a boolean value.
172 * @return a {@code Boolean} instance representing {@code b}.
173 * @since 1.4
174 */
175 @IntrinsicCandidate
176 @DeserializeConstructor
177 public static Boolean valueOf(boolean b) {
178 return (b ? TRUE : FALSE);
179 }
180
181 /**
182 * Returns a {@code Boolean} with a value represented by the
183 * specified string. The {@code Boolean} returned represents a
184 * true value if the string argument is not {@code null}
185 * and is equal, ignoring case, to the string {@code "true"}.
186 * Otherwise, a false value is returned, including for a null
187 * argument.
188 *
189 * @param s a string.
190 * @return the {@code Boolean} value represented by the string.
191 */
192 public static Boolean valueOf(String s) {
193 return parseBoolean(s) ? TRUE : FALSE;
194 }
195
196 /**
197 * Returns a {@code String} object representing the specified
198 * boolean. If the specified boolean is {@code true}, then
199 * the string {@code "true"} will be returned, otherwise the
200 * string {@code "false"} will be returned.
201 *
202 * @param b the boolean to be converted
203 * @return the string representation of the specified {@code boolean}
204 * @since 1.4
205 */
206 public static String toString(boolean b) {
207 return String.valueOf(b);
208 }
209
210 /**
211 * Returns a {@code String} object representing this Boolean's
212 * value. If this object represents the value {@code true},
213 * a string equal to {@code "true"} is returned. Otherwise, a
214 * string equal to {@code "false"} is returned.
215 *
216 * @return a string representation of this object.
217 */
218 @Override
219 public String toString() {
220 return String.valueOf(value);
221 }
222
223 /**
224 * Returns a hash code for this {@code Boolean} object.
225 *
226 * @return the integer {@code 1231} if this object represents
227 * {@code true}; returns the integer {@code 1237} if this
228 * object represents {@code false}.
229 */
230 @Override
231 public int hashCode() {
232 return Boolean.hashCode(value);
233 }
234
235 /**
236 * Returns a hash code for a {@code boolean} value; compatible with
237 * {@code Boolean.hashCode()}.
238 *
239 * @param value the value to hash
240 * @return a hash code value for a {@code boolean} value.
241 * @since 1.8
242 */
243 public static int hashCode(boolean value) {
244 return value ? 1231 : 1237;
245 }
246
247 /**
248 * Returns {@code true} if and only if the argument is not
249 * {@code null} and is a {@code Boolean} object that
250 * represents the same {@code boolean} value as this object.
251 *
252 * @param obj the object to compare with.
253 * @return {@code true} if the Boolean objects represent the
254 * same value; {@code false} otherwise.
255 */
256 public boolean equals(Object obj) {
257 if (obj instanceof Boolean) {
258 return value == ((Boolean)obj).booleanValue();
259 }
260 return false;
261 }
262
263 /**
264 * Returns {@code true} if and only if the system property named
265 * by the argument exists and is equal to, ignoring case, the
266 * string {@code "true"}.
267 * A system property is accessible through {@code getProperty}, a
268 * method defined by the {@code System} class. <p> If there is no
269 * property with the specified name, or if the specified name is
270 * empty or null, then {@code false} is returned.
271 *
272 * @param name the system property name.
273 * @return the {@code boolean} value of the system property.
274 * @throws SecurityException for the same reasons as
275 * {@link System#getProperty(String) System.getProperty}
276 * @see java.lang.System#getProperty(java.lang.String)
277 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
278 */
279 public static boolean getBoolean(String name) {
280 boolean result = false;
281 try {
282 result = parseBoolean(System.getProperty(name));
283 } catch (IllegalArgumentException | NullPointerException e) {
284 }
285 return result;
286 }
287
288 /**
289 * Compares this {@code Boolean} instance with another.
290 *
291 * @param b the {@code Boolean} instance to be compared
292 * @return zero if this object represents the same boolean value as the
293 * argument; a positive value if this object represents true
294 * and the argument represents false; and a negative value if
295 * this object represents false and the argument represents true
296 * @throws NullPointerException if the argument is {@code null}
297 * @see Comparable
298 * @since 1.5
299 */
300 public int compareTo(Boolean b) {
301 return compare(this.value, b.value);
302 }
303
304 /**
305 * Compares two {@code boolean} values.
306 * The value returned is identical to what would be returned by:
307 * <pre>
308 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y))
309 * </pre>
310 *
311 * @param x the first {@code boolean} to compare
312 * @param y the second {@code boolean} to compare
313 * @return the value {@code 0} if {@code x == y};
314 * a value less than {@code 0} if {@code !x && y}; and
315 * a value greater than {@code 0} if {@code x && !y}
316 * @since 1.7
317 */
318 public static int compare(boolean x, boolean y) {
319 return (x == y) ? 0 : (x ? 1 : -1);
320 }
321
322 /**
323 * Returns the result of applying the logical AND operator to the
324 * specified {@code boolean} operands.
325 *
326 * @param a the first operand
327 * @param b the second operand
328 * @return the logical AND of {@code a} and {@code b}
329 * @see java.util.function.BinaryOperator
330 * @since 1.8
331 */
332 public static boolean logicalAnd(boolean a, boolean b) {
333 return a && b;
334 }
335
336 /**
337 * Returns the result of applying the logical OR operator to the
338 * specified {@code boolean} operands.
339 *
340 * @param a the first operand
341 * @param b the second operand
342 * @return the logical OR of {@code a} and {@code b}
343 * @see java.util.function.BinaryOperator
344 * @since 1.8
345 */
346 public static boolean logicalOr(boolean a, boolean b) {
347 return a || b;
348 }
349
350 /**
351 * Returns the result of applying the logical XOR operator to the
352 * specified {@code boolean} operands.
353 *
354 * @param a the first operand
355 * @param b the second operand
356 * @return the logical XOR of {@code a} and {@code b}
357 * @see java.util.function.BinaryOperator
358 * @since 1.8
359 */
360 public static boolean logicalXor(boolean a, boolean b) {
361 return a ^ b;
362 }
363
364 /**
365 * Returns an {@link Optional} containing the nominal descriptor for this
366 * instance.
367 *
368 * @return an {@link Optional} describing the {@linkplain Boolean} instance
369 * @since 15
370 */
371 @Override
372 public Optional<DynamicConstantDesc<Boolean>> describeConstable() {
373 return Optional.of(value ? ConstantDescs.TRUE : ConstantDescs.FALSE);
374 }
375 }