1 /*
2 * Copyright (c) 2009, 2023, 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.util;
27
28 import jdk.internal.util.Preconditions;
29 import jdk.internal.vm.annotation.ForceInline;
30
31 import java.util.function.Supplier;
32
33 /**
34 * This class consists of {@code static} utility methods for operating
35 * on objects, or checking certain conditions before operation. These utilities
36 * include {@code null}-safe or {@code null}-tolerant methods for computing the
37 * hash code of an object, returning a string for an object, comparing two
38 * objects, and checking if indexes or sub-range values are out of bounds.
39 *
40 * @since 1.7
41 */
42 public final class Objects {
43 private Objects() {
44 throw new AssertionError("No java.util.Objects instances for you!");
45 }
46
47 /**
141
142 /**
143 * {@return the result of calling {@code toString} on the first
144 * argument if the first argument is not {@code null} and the
145 * second argument otherwise}
146 *
147 * @param o an object
148 * @param nullDefault string to return if the first argument is
149 * {@code null}
150 * @see Objects#toString(Object)
151 */
152 public static String toString(Object o, String nullDefault) {
153 return (o != null) ? o.toString() : nullDefault;
154 }
155
156 /**
157 * {@return a string equivalent to the string returned by {@code
158 * Object.toString} if that method and {@code hashCode} are not
159 * overridden}
160 *
161 * @implNote
162 * This method constructs a string for an object without calling
163 * any overridable methods of the object.
164 *
165 * @implSpec
166 * The method returns a string equivalent to:<br>
167 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
168 *
169 * @param o an object
170 * @throws NullPointerException if the argument is null
171 * @see Object#toString
172 * @see System#identityHashCode(Object)
173 * @since 19
174 */
175 public static String toIdentityString(Object o) {
176 requireNonNull(o);
177 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
178 }
179
180 /**
181 * {@return 0 if the arguments are identical and {@code
182 * c.compare(a, b)} otherwise}
183 * Consequently, if both arguments are {@code null} 0
184 * is returned.
185 *
186 * <p>Note that if one of the arguments is {@code null}, a {@code
187 * NullPointerException} may or may not be thrown depending on
188 * what ordering policy, if any, the {@link Comparator Comparator}
189 * chooses to have for {@code null} values.
190 *
191 * @param <T> the type of the objects being compared
192 * @param a an object
193 * @param b an object to be compared with {@code a}
194 * @param c the {@code Comparator} to compare the first two arguments
195 * @see Comparable
196 * @see Comparator
197 */
198 public static <T> int compare(T a, T b, Comparator<? super T> c) {
199 return (a == b) ? 0 : c.compare(a, b);
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1 /*
2 * Copyright (c) 2009, 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.util;
27
28 import jdk.internal.javac.PreviewFeature;
29 import jdk.internal.util.Preconditions;
30 import jdk.internal.vm.annotation.ForceInline;
31
32 import java.util.function.Supplier;
33
34 /**
35 * This class consists of {@code static} utility methods for operating
36 * on objects, or checking certain conditions before operation. These utilities
37 * include {@code null}-safe or {@code null}-tolerant methods for computing the
38 * hash code of an object, returning a string for an object, comparing two
39 * objects, and checking if indexes or sub-range values are out of bounds.
40 *
41 * @since 1.7
42 */
43 public final class Objects {
44 private Objects() {
45 throw new AssertionError("No java.util.Objects instances for you!");
46 }
47
48 /**
142
143 /**
144 * {@return the result of calling {@code toString} on the first
145 * argument if the first argument is not {@code null} and the
146 * second argument otherwise}
147 *
148 * @param o an object
149 * @param nullDefault string to return if the first argument is
150 * {@code null}
151 * @see Objects#toString(Object)
152 */
153 public static String toString(Object o, String nullDefault) {
154 return (o != null) ? o.toString() : nullDefault;
155 }
156
157 /**
158 * {@return a string equivalent to the string returned by {@code
159 * Object.toString} if that method and {@code hashCode} are not
160 * overridden}
161 *
162 * @apiNote
163 * <div class="preview-block">
164 * <div class="preview-comment">
165 * Note that, like ==, the hash code string exposes information about a value object's
166 * private fields that might otherwise be hidden by an identity object.
167 * Developers should be cautious about storing sensitive secrets in value object fields.
168 * </div>
169 * </div>
170 *
171 * @implNote
172 * This method constructs a string for an object without calling
173 * any overridable methods of the object.
174 *
175 * @implSpec
176 * The method returns a string equivalent to:<br>
177 * {@code o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o))}
178 *
179 * @param o an object
180 * @throws NullPointerException if the argument is null
181 * @see Object#toString
182 * @see System#identityHashCode(Object)
183 * @since 19
184 */
185 public static String toIdentityString(Object o) {
186 requireNonNull(o);
187 return o.getClass().getName() + "@" + Integer.toHexString(System.identityHashCode(o));
188 }
189
190 /**
191 * {@return {@code true} if the input is a non-null reference
192 * to an object with identity, and {@code false} otherwise}
193 *
194 * <p>If the object is an instance of a concrete {@linkplain Class#isValue()
195 * value class}, it does not have identity and the result will be
196 * {@code false}. All other objects, including arrays, are identity objects
197 * and the result will be {@code true}.
198 *
199 * <p>This method returns {@code false} if and only if the parameter is
200 * {@code null} or if the parameter represents a value object when preview
201 * features are enabled. All objects are identity objects when preview
202 * features are disabled; consequently, this method behaves the same as
203 * {@link #nonNull Objects.nonNull} when preview features are disabled.
204 *
205 * @apiNote
206 * If the parameter is {@code null}, there is no object
207 * and hence no identity; the result is {@code false}.
208 * To test for a value object use:
209 * {@snippet type="java" :
210 * if (obj != null && !Objects.hasIdentity(obj)) {
211 * // obj is a non-null value object
212 * }
213 * }
214 * @param obj an object or {@code null}
215 * @since 28
216 */
217 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective=true)
218 public static boolean hasIdentity(Object obj) {
219 return (obj == null) ? false : !obj.getClass().isValue();
220 }
221
222 /**
223 * Checks that the specified object reference is an identity object.
224 * <p>
225 * This method throws an {@code IdentityException} if and only if the
226 * parameter represents a value object when preview features are enabled.
227 * All objects are identity objects when preview features are disabled;
228 * consequently, this method behaves the same as {@link #requireNonNull(Object)
229 * Objects.requireNonNull} when preview features are disabled.
230 *
231 * @param obj the object reference to check for identity
232 * @param <T> the type of the reference
233 * @return {@code obj} if {@code obj} is an identity object
234 * @throws NullPointerException if {@code obj} is {@code null}
235 * @throws IdentityException if {@code obj} is not an identity object
236 * @since 28
237 */
238 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective = true)
239 @ForceInline
240 public static <T> T requireIdentity(T obj) {
241 Objects.requireNonNull(obj);
242 if (!hasIdentity(obj))
243 throw new IdentityException(obj.getClass().getName() + " is not an identity class");
244 return obj;
245 }
246
247 /**
248 * Checks that the specified object reference is an identity object.
249 * <p>
250 * This method throws an {@code IdentityException} if and only if the
251 * parameter represents a value object when preview features are enabled.
252 * All objects are identity objects when preview features are disabled;
253 * consequently, this method behaves the same as {@link #requireNonNull(Object, String)
254 * Objects.requireNonNull} when preview features are disabled.
255 *
256 * @param obj the object reference to check for identity
257 * @param message detail message to be used in the event that an
258 * {@code IdentityException} is thrown; may be null
259 * @param <T> the type of the reference
260 * @return {@code obj} if {@code obj} is an identity object
261 * @throws NullPointerException if {@code obj} is {@code null}
262 * @throws IdentityException if {@code obj} is not an identity object
263 * @since 28
264 */
265 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective = true)
266 @ForceInline
267 public static <T> T requireIdentity(T obj, String message) {
268 Objects.requireNonNull(obj);
269 if (!hasIdentity(obj))
270 throw new IdentityException(message);
271 return obj;
272 }
273
274 /**
275 * Checks that the specified object reference is an identity object.
276 * <p>
277 * This method throws an {@code IdentityException} if and only if the
278 * parameter represents a value object when preview features are enabled.
279 * All objects are identity objects when preview features are disabled;
280 * consequently, this method behaves the same as {@link #requireNonNull(Object, Supplier)
281 * Objects.requireNonNull} when preview features are disabled.
282 *
283 * @param obj the object reference to check for identity
284 * @param messageSupplier supplier of the detail message to be
285 * used in the event that an {@code IdentityException} is thrown; may be null
286 * @param <T> the type of the reference
287 * @return {@code obj} if {@code obj} is an identity object
288 * @throws NullPointerException if {@code obj} is {@code null}
289 * @throws IdentityException if {@code obj} is not an identity object
290 * @since 28
291 */
292 @PreviewFeature(feature = PreviewFeature.Feature.VALUE_OBJECTS, reflective = true)
293 @ForceInline
294 public static <T> T requireIdentity(T obj, Supplier<String> messageSupplier) {
295 Objects.requireNonNull(obj);
296 if (!hasIdentity(obj))
297 throw new IdentityException(messageSupplier == null ?
298 null : messageSupplier.get());
299 return obj;
300 }
301
302 /**
303 * {@return 0 if the arguments are identical and {@code
304 * c.compare(a, b)} otherwise}
305 * Consequently, if both arguments are {@code null} 0
306 * is returned.
307 *
308 * <p>Note that if one of the arguments is {@code null}, a {@code
309 * NullPointerException} may or may not be thrown depending on
310 * what ordering policy, if any, the {@link Comparator Comparator}
311 * chooses to have for {@code null} values.
312 *
313 * @param <T> the type of the objects being compared
314 * @param a an object
315 * @param b an object to be compared with {@code a}
316 * @param c the {@code Comparator} to compare the first two arguments
317 * @see Comparable
318 * @see Comparator
319 */
320 public static <T> int compare(T a, T b, Comparator<? super T> c) {
321 return (a == b) ? 0 : c.compare(a, b);
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