diff -r 5d25a1df3540 -r d382dacfd73f rt/emul/compact/src/main/java/java/util/Objects.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/rt/emul/compact/src/main/java/java/util/Objects.java Tue Feb 26 16:54:16 2013 +0100 @@ -0,0 +1,229 @@ +/* + * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. Oracle designates this + * particular file as subject to the "Classpath" exception as provided + * by Oracle in the LICENSE file that accompanied this code. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + */ + +package java.util; + +/** + * This class consists of {@code static} utility methods for operating + * on objects. These utilities include {@code null}-safe or {@code + * null}-tolerant methods for computing the hash code of an object, + * returning a string for an object, and comparing two objects. + * + * @since 1.7 + */ +public final class Objects { + private Objects() { + throw new AssertionError("No java.util.Objects instances for you!"); + } + + /** + * Returns {@code true} if the arguments are equal to each other + * and {@code false} otherwise. + * Consequently, if both arguments are {@code null}, {@code true} + * is returned and if exactly one argument is {@code null}, {@code + * false} is returned. Otherwise, equality is determined by using + * the {@link Object#equals equals} method of the first + * argument. + * + * @param a an object + * @param b an object to be compared with {@code a} for equality + * @return {@code true} if the arguments are equal to each other + * and {@code false} otherwise + * @see Object#equals(Object) + */ + public static boolean equals(Object a, Object b) { + return (a == b) || (a != null && a.equals(b)); + } + + /** + * Returns {@code true} if the arguments are deeply equal to each other + * and {@code false} otherwise. + * + * Two {@code null} values are deeply equal. If both arguments are + * arrays, the algorithm in {@link Arrays#deepEquals(Object[], + * Object[]) Arrays.deepEquals} is used to determine equality. + * Otherwise, equality is determined by using the {@link + * Object#equals equals} method of the first argument. + * + * @param a an object + * @param b an object to be compared with {@code a} for deep equality + * @return {@code true} if the arguments are deeply equal to each other + * and {@code false} otherwise + * @see Arrays#deepEquals(Object[], Object[]) + * @see Objects#equals(Object, Object) + */ + public static boolean deepEquals(Object a, Object b) { + if (a == b) + return true; + else if (a == null || b == null) + return false; + else + return Arrays.deepEquals0(a, b); + } + + /** + * Returns the hash code of a non-{@code null} argument and 0 for + * a {@code null} argument. + * + * @param o an object + * @return the hash code of a non-{@code null} argument and 0 for + * a {@code null} argument + * @see Object#hashCode + */ + public static int hashCode(Object o) { + return o != null ? o.hashCode() : 0; + } + + /** + * Generates a hash code for a sequence of input values. The hash + * code is generated as if all the input values were placed into an + * array, and that array were hashed by calling {@link + * Arrays#hashCode(Object[])}. + * + *
This method is useful for implementing {@link + * Object#hashCode()} on objects containing multiple fields. For + * example, if an object that has three fields, {@code x}, {@code + * y}, and {@code z}, one could write: + * + *
+ * + * Warning: When a single object reference is supplied, the returned + * value does not equal the hash code of that object reference. This + * value can be computed by calling {@link #hashCode(Object)}. + * + * @param values the values to be hashed + * @return a hash value of the sequence of input values + * @see Arrays#hashCode(Object[]) + * @see List#hashCode + */ + public static int hash(Object... values) { + return Arrays.hashCode(values); + } + + /** + * Returns the result of calling {@code toString} for a non-{@code + * null} argument and {@code "null"} for a {@code null} argument. + * + * @param o an object + * @return the result of calling {@code toString} for a non-{@code + * null} argument and {@code "null"} for a {@code null} argument + * @see Object#toString + * @see String#valueOf(Object) + */ + public static String toString(Object o) { + return String.valueOf(o); + } + + /** + * Returns the result of calling {@code toString} on the first + * argument if the first argument is not {@code null} and returns + * the second argument otherwise. + * + * @param o an object + * @param nullDefault string to return if the first argument is + * {@code null} + * @return the result of calling {@code toString} on the first + * argument if it is not {@code null} and the second argument + * otherwise. + * @see Objects#toString(Object) + */ + public static String toString(Object o, String nullDefault) { + return (o != null) ? o.toString() : nullDefault; + } + + /** + * Returns 0 if the arguments are identical and {@code + * c.compare(a, b)} otherwise. + * Consequently, if both arguments are {@code null} 0 + * is returned. + * + *+ * @Override public int hashCode() { + * return Objects.hash(x, y, z); + * } + *
Note that if one of the arguments is {@code null}, a {@code
+ * NullPointerException} may or may not be thrown depending on
+ * what ordering policy, if any, the {@link Comparator Comparator}
+ * chooses to have for {@code null} values.
+ *
+ * @param
+ *
+ * @param obj the object reference to check for nullity
+ * @param
+ * public Foo(Bar bar) {
+ * this.bar = Objects.requireNonNull(bar);
+ * }
+ *
+ *
+ * @param obj the object reference to check for nullity
+ * @param message detail message to be used in the event that a {@code
+ * NullPointerException} is thrown
+ * @param
+ * public Foo(Bar bar, Baz baz) {
+ * this.bar = Objects.requireNonNull(bar, "bar must not be null");
+ * this.baz = Objects.requireNonNull(baz, "baz must not be null");
+ * }
+ *