Hello! equals() spec says:
The implicitly provided implementation returns {@code true} if and * only if the argument is an instance of the same record type as this object, * and each component of this record is equal to the corresponding component * of the argument, according to {@link Object#equals(Object)} for components * whose types are reference types, and {@code ==} for components whose * types are primitive types. * This contradicts the class spec for float/double fields (in particular, NaN values): * <p>For all record classes, the following invariant must hold: if a record R's * components are {@code c1, c2, ... cn}, then if a record instance is copied * as follows: * <pre> * R copy = new R(r.c1(), r.c2(), ..., r.cn()); * </pre> * then it must be the case that {@code r.equals(copy)}. E.g. record R(double d) {} R r1 = new R(Double.NaN); R r2 = new R(r1.d()); assert r1.equals(r2); // fails as R.d is a primitive field and r1.d != r2.d With best regards, Tagir Valeev. On Fri, Aug 16, 2019 at 12:15 AM Tagir Valeev <amae...@gmail.com> wrote: > Hello! > > >a private static field corresponding to each component > > Final instead of static? > > With best regards, > Tagir Valeev > > пт, 16 авг. 2019 г., 0:06 Brian Goetz <brian.go...@oracle.com>: > >> Draft spec, please comment. >> >> >> /* * Copyright (c) 2019, 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.lang; >> /** * This is the common base class of all Java language record classes. * * >> <p>More information about records, including descriptions of the * >> implicitly declared methods synthesized by the compiler, can be * found in >> section 8.10 of * <cite>The Java™ Language Specification</cite>. * * >> <p>A <em>record class</em> is a shallowly immutable, transparent carrier for >> * a fixed set of values, called the <em>record components</em>. The >> Java™ * language provides concise syntax for declaring record classes, >> whereby the * record components are declared in the record header. The list >> of record * components declared in the record header form the <em>record >> descriptor</em>. * * <p>A record class has the following mandated members: a >> public <em>canonical * constructor</em>, whose descriptor is the same as the >> record descriptor; * a private static field corresponding to each component, >> whose name and * type are the same as that of the component; a public >> accessor method * corresponding to each component, whose name and return >> type are the same as * that of the component. If not explicitly declared in >> the body of the record, * implicit implementations for these members are >> provided. * * <p>The implicit declaration of the canonical constructor >> initializes the * component fields from the corresponding constructor >> arguments. The implicit * declaration of the accessor methods returns the >> value of the corresponding * component field. The implicit declaration of >> the {@link Object#equals(Object)}, * {@link Object#hashCode()}, and {@link >> Object#toString()} methods are derived * from all of the component fields. * >> * <p>The primary reasons to provide an explicit declaration for the * >> canonical constructor or accessor methods are to validate constructor * >> arguments, perform defensive copies on mutable components, or normalize >> groups * of components (such as reducing a rational number to lowest terms.) >> If any * of these are provided explicitly. * * <p>For all record classes, >> the following invariant must hold: if a record R's * components are {@code >> c1, c2, ... cn}, then if a record instance is copied * as follows: * <pre> * >> R copy = new R(r.c1(), r.c2(), ..., r.cn()); * </pre> * then it must be >> the case that {@code r.equals(copy)}. * * @jls 8.10 * @since 14 */public >> abstract class Record { >> /** * Indicates whether some other object is "equal to" this one. >> In addition * to the general contract of {@link Object#equals(Object)}, >> * record classes must further participate in the invariant that when >> * a record instance is "copied" by passing the result of the record >> component * accessor methods to the canonical constructor, the resulting >> copy is * equal to the original instance. * * @implNote * >> The implicitly provided implementation returns {@code true} if and * >> only if the argument is an instance of the same record type as this object, >> * and each component of this record is equal to the corresponding >> component * of the argument, according to {@link Object#equals(Object)} >> for components * whose types are reference types, and {@code ==} for >> components whose * types are primitive types. * * @see >> Object#equals(Object) * * @param obj the reference object with >> which to compare. * @return {@code true} if this object is the same as >> the obj * argument; {@code false} otherwise. */ >> @Override public abstract boolean equals(Object obj); >> >> /** * {@inheritDoc} * * @implNote * The implicitly >> provided implementation returns a hash code value derived * by combining >> the hash code value for all the components, according to * {@link >> Object#hashCode()} for components whose types are reference types, * or >> the primitive wrapper hash code for components whose types are primitive >> * types. * * @see Object#hashCode() * * @return a >> hash code value for this object. */ @Override public abstract int >> hashCode(); >> >> /** * {@inheritDoc} * * @implNote * The implicitly >> provided implementation returns a string that is derived * from the name >> of the record class and the names and string representations * of all >> the components, according to {@link Object#toString()} for components * >> whose types are reference types, and the primitive wrapper {@code toString} >> * method for components whose types are primitive types. * * @see >> Object#toString() () * * @return a string representation of the >> object. */ @Override public abstract String toString(); >> } >> >>