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.vm.annotation.IntrinsicCandidate;
29
30 import java.lang.constant.Constable;
31 import java.lang.constant.ConstantDesc;
32 import java.lang.constant.ConstantDescs;
33 import java.lang.constant.DynamicConstantDesc;
34 import java.util.Optional;
35
36 import static java.lang.constant.ConstantDescs.BSM_GET_STATIC_FINAL;
37 import static java.lang.constant.ConstantDescs.CD_Boolean;
38
39 /**
40 * The Boolean class wraps a value of the primitive type
41 * {@code boolean} in an object. An object of type
42 * {@code Boolean} contains a single field whose type is
43 * {@code boolean}.
44 *
45 * <p>In addition, this class provides many methods for
46 * converting a {@code boolean} to a {@code String} and a
47 * {@code String} to a {@code boolean}, as well as other
48 * constants and methods useful when dealing with a
49 * {@code boolean}.
50 *
51 * <p>This is a <a href="{@docRoot}/java.base/java/lang/doc-files/ValueBased.html">value-based</a>
52 * class; programmers should treat instances that are
53 * {@linkplain #equals(Object) equal} as interchangeable and should not
54 * use instances for synchronization, or unpredictable behavior may
55 * occur. For example, in a future release, synchronization may fail.
56 *
57 * @author Arthur van Hoff
58 * @since 1.0
59 */
60 @jdk.internal.ValueBased
61 public final class Boolean implements java.io.Serializable,
62 Comparable<Boolean>, Constable
63 {
64 /**
65 * The {@code Boolean} object corresponding to the primitive
66 * value {@code true}.
67 */
68 public static final Boolean TRUE = new Boolean(true);
69
70 /**
71 * The {@code Boolean} object corresponding to the primitive
72 * value {@code false}.
73 */
74 public static final Boolean FALSE = new Boolean(false);
75
76 /**
77 * The Class object representing the primitive type boolean.
78 *
79 * @since 1.1
80 */
81 @SuppressWarnings("unchecked")
82 public static final Class<Boolean> TYPE = (Class<Boolean>) Class.getPrimitiveClass("boolean");
83
84 /**
85 * The value of the Boolean.
86 *
87 * @serial
88 */
89 private final boolean value;
90
91 /** use serialVersionUID from JDK 1.0.2 for interoperability */
92 @java.io.Serial
93 private static final long serialVersionUID = -3665804199014368530L;
94
95 /**
96 * Allocates a {@code Boolean} object representing the
97 * {@code value} argument.
98 *
99 * @param value the value of the {@code Boolean}.
100 *
101 * @deprecated
102 * It is rarely appropriate to use this constructor. The static factory
103 * {@link #valueOf(boolean)} is generally a better choice, as it is
104 * likely to yield significantly better space and time performance.
105 * Also consider using the final fields {@link #TRUE} and {@link #FALSE}
106 * if possible.
107 */
108 @Deprecated(since="9", forRemoval = true)
109 public Boolean(boolean value) {
110 this.value = value;
111 }
112
113 /**
114 * Allocates a {@code Boolean} object representing the value
115 * {@code true} if the string argument is not {@code null}
116 * and is equal, ignoring case, to the string {@code "true"}.
117 * Otherwise, allocates a {@code Boolean} object representing the
118 * value {@code false}.
119 *
120 * @param s the string to be converted to a {@code Boolean}.
121 *
122 * @deprecated
123 * It is rarely appropriate to use this constructor.
124 * Use {@link #parseBoolean(String)} to convert a string to a
125 * {@code boolean} primitive, or use {@link #valueOf(String)}
126 * to convert a string to a {@code Boolean} object.
127 */
128 @Deprecated(since="9", forRemoval = true)
129 public Boolean(String s) {
130 this(parseBoolean(s));
131 }
132
133 /**
134 * Parses the string argument as a boolean. The {@code boolean}
135 * returned represents the value {@code true} if the string argument
136 * is not {@code null} and is equal, ignoring case, to the string
137 * {@code "true"}.
138 * Otherwise, a false value is returned, including for a null
139 * argument.<p>
140 * Example: {@code Boolean.parseBoolean("True")} returns {@code true}.<br>
141 * Example: {@code Boolean.parseBoolean("yes")} returns {@code false}.
142 *
143 * @param s the {@code String} containing the boolean
144 * representation to be parsed
145 * @return the boolean represented by the string argument
146 * @since 1.5
147 */
148 public static boolean parseBoolean(String s) {
149 return "true".equalsIgnoreCase(s);
150 }
151
152 /**
153 * Returns the value of this {@code Boolean} object as a boolean
154 * primitive.
155 *
156 * @return the primitive {@code boolean} value of this object.
157 */
158 @IntrinsicCandidate
159 public boolean booleanValue() {
160 return value;
161 }
162
163 /**
164 * Returns a {@code Boolean} instance representing the specified
165 * {@code boolean} value. If the specified {@code boolean} value
166 * is {@code true}, this method returns {@code Boolean.TRUE};
167 * if it is {@code false}, this method returns {@code Boolean.FALSE}.
168 * If a new {@code Boolean} instance is not required, this method
169 * should generally be used in preference to the constructor
170 * {@link #Boolean(boolean)}, as this method is likely to yield
171 * significantly better space and time performance.
172 *
173 * @param b a boolean value.
174 * @return a {@code Boolean} instance representing {@code b}.
175 * @since 1.4
176 */
177 @IntrinsicCandidate
178 public static Boolean valueOf(boolean b) {
179 return (b ? TRUE : FALSE);
180 }
181
182 /**
183 * Returns a {@code Boolean} with a value represented by the
184 * specified string. The {@code Boolean} returned represents a
185 * true value if the string argument is not {@code null}
186 * and is equal, ignoring case, to the string {@code "true"}.
187 * Otherwise, a false value is returned, including for a null
188 * argument.
189 *
190 * @param s a string.
191 * @return the {@code Boolean} value represented by the string.
192 */
193 public static Boolean valueOf(String s) {
194 return parseBoolean(s) ? TRUE : FALSE;
195 }
196
197 /**
198 * Returns a {@code String} object representing the specified
199 * boolean. If the specified boolean is {@code true}, then
200 * the string {@code "true"} will be returned, otherwise the
201 * string {@code "false"} will be returned.
202 *
203 * @param b the boolean to be converted
204 * @return the string representation of the specified {@code boolean}
205 * @since 1.4
206 */
207 public static String toString(boolean b) {
208 return String.valueOf(b);
209 }
210
211 /**
212 * Returns a {@code String} object representing this Boolean's
213 * value. If this object represents the value {@code true},
214 * a string equal to {@code "true"} is returned. Otherwise, a
215 * string equal to {@code "false"} is returned.
216 *
217 * @return a string representation of this object.
218 */
219 @Override
220 public String toString() {
221 return String.valueOf(value);
222 }
223
224 /**
225 * Returns a hash code for this {@code Boolean} object.
226 *
227 * @return the integer {@code 1231} if this object represents
228 * {@code true}; returns the integer {@code 1237} if this
229 * object represents {@code false}.
230 */
231 @Override
232 public int hashCode() {
233 return Boolean.hashCode(value);
234 }
235
236 /**
237 * Returns a hash code for a {@code boolean} value; compatible with
238 * {@code Boolean.hashCode()}.
239 *
240 * @param value the value to hash
241 * @return a hash code value for a {@code boolean} value.
242 * @since 1.8
243 */
244 public static int hashCode(boolean value) {
245 return value ? 1231 : 1237;
246 }
247
248 /**
249 * Returns {@code true} if and only if the argument is not
250 * {@code null} and is a {@code Boolean} object that
251 * represents the same {@code boolean} value as this object.
252 *
253 * @param obj the object to compare with.
254 * @return {@code true} if the Boolean objects represent the
255 * same value; {@code false} otherwise.
256 */
257 public boolean equals(Object obj) {
258 if (obj instanceof Boolean) {
259 return value == ((Boolean)obj).booleanValue();
260 }
261 return false;
262 }
263
264 /**
265 * Returns {@code true} if and only if the system property named
266 * by the argument exists and is equal to, ignoring case, the
267 * string {@code "true"}.
268 * A system property is accessible through {@code getProperty}, a
269 * method defined by the {@code System} class. <p> If there is no
270 * property with the specified name, or if the specified name is
271 * empty or null, then {@code false} is returned.
272 *
273 * @param name the system property name.
274 * @return the {@code boolean} value of the system property.
275 * @throws SecurityException for the same reasons as
276 * {@link System#getProperty(String) System.getProperty}
277 * @see java.lang.System#getProperty(java.lang.String)
278 * @see java.lang.System#getProperty(java.lang.String, java.lang.String)
279 */
280 public static boolean getBoolean(String name) {
281 boolean result = false;
282 try {
283 result = parseBoolean(System.getProperty(name));
284 } catch (IllegalArgumentException | NullPointerException e) {
285 }
286 return result;
287 }
288
289 /**
290 * Compares this {@code Boolean} instance with another.
291 *
292 * @param b the {@code Boolean} instance to be compared
293 * @return zero if this object represents the same boolean value as the
294 * argument; a positive value if this object represents true
295 * and the argument represents false; and a negative value if
296 * this object represents false and the argument represents true
297 * @throws NullPointerException if the argument is {@code null}
298 * @see Comparable
299 * @since 1.5
300 */
301 public int compareTo(Boolean b) {
302 return compare(this.value, b.value);
303 }
304
305 /**
306 * Compares two {@code boolean} values.
307 * The value returned is identical to what would be returned by:
308 * <pre>
309 * Boolean.valueOf(x).compareTo(Boolean.valueOf(y))
310 * </pre>
311 *
312 * @param x the first {@code boolean} to compare
313 * @param y the second {@code boolean} to compare
314 * @return the value {@code 0} if {@code x == y};
315 * a value less than {@code 0} if {@code !x && y}; and
316 * a value greater than {@code 0} if {@code x && !y}
317 * @since 1.7
318 */
319 public static int compare(boolean x, boolean y) {
320 return (x == y) ? 0 : (x ? 1 : -1);
321 }
322
323 /**
324 * Returns the result of applying the logical AND operator to the
325 * specified {@code boolean} operands.
326 *
327 * @param a the first operand
328 * @param b the second operand
329 * @return the logical AND of {@code a} and {@code b}
330 * @see java.util.function.BinaryOperator
331 * @since 1.8
332 */
333 public static boolean logicalAnd(boolean a, boolean b) {
334 return a && b;
335 }
336
337 /**
338 * Returns the result of applying the logical OR operator to the
339 * specified {@code boolean} operands.
340 *
341 * @param a the first operand
342 * @param b the second operand
343 * @return the logical OR of {@code a} and {@code b}
344 * @see java.util.function.BinaryOperator
345 * @since 1.8
346 */
347 public static boolean logicalOr(boolean a, boolean b) {
348 return a || b;
349 }
350
351 /**
352 * Returns the result of applying the logical XOR operator to the
353 * specified {@code boolean} operands.
354 *
355 * @param a the first operand
356 * @param b the second operand
357 * @return the logical XOR of {@code a} and {@code b}
358 * @see java.util.function.BinaryOperator
359 * @since 1.8
360 */
361 public static boolean logicalXor(boolean a, boolean b) {
362 return a ^ b;
363 }
364
365 /**
366 * Returns an {@link Optional} containing the nominal descriptor for this
367 * instance.
368 *
369 * @return an {@link Optional} describing the {@linkplain Boolean} instance
370 * @since 15
371 */
372 @Override
373 public Optional<DynamicConstantDesc<Boolean>> describeConstable() {
374 return Optional.of(value ? ConstantDescs.TRUE : ConstantDescs.FALSE);
375 }
376 }