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Apache Commons Lang, a package of Java utility classes for the classes that are in java.lang's hierarchy, or are considered to be so standard as to justify existence in java.lang. The code is tested using the latest revision of the JDK for supported LTS releases: 8, 11, 17 and 21 currently. See https://github.com/apache/commons-lang/blob/master/.github/workflows/maven.yml Please ensure your build environment is up-to-date and kindly report any build issues.

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.commons.lang3.builder;

// adapted from org.apache.axis.utils.IDKey

/**
 * Wrap an identity key (System.identityHashCode())
 * so that an object can only be equal() to itself.
 *
 * This is necessary to disambiguate the occasional duplicate
 * identityHashCodes that can occur.
 */
final class IDKey {
        private final Object value;
        private final int id;

        /**
         * Constructor for IDKey
         * @param _value The value
         */
        IDKey(final Object _value) {
            // This is the Object hash code
            id = System.identityHashCode(_value);
            // There have been some cases (LANG-459) that return the
            // same identity hash code for different objects.  So
            // the value is also added to disambiguate these cases.
            value = _value;
        }

        /**
         * returns hash code - i.e. the system identity hashcode.
         * @return the hashcode
         */
        @Override
        public int hashCode() {
           return id;
        }

        /**
         * checks if instances are equal
         * @param other The other object to compare to
         * @return if the instances are for the same object
         */
        @Override
        public boolean equals(final Object other) {
            if (!(other instanceof IDKey)) {
                return false;
            }
            final IDKey idKey = (IDKey) other;
            if (id != idKey.id) {
                return false;
            }
            // Note that identity equals is used.
            return value == idKey.value;
         }
}




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