test/java/util/IdentityHashMap/DistinctEntrySetElements.java

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
 * 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.
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/*
 * Portions Copyright (c) 2011 IBM Corporation
 */

/*
 * @test
 * @bug 6312706
 * @summary Sets from Map.entrySet() return distinct objects for each Entry
 * @author Neil Richards <neil.richards@ngmr.net>, <neil_richards@uk.ibm.com>
 */

import java.util.IdentityHashMap;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;

public class DistinctEntrySetElements {
    public static void main(String[] args) throws Exception {
        final IdentityHashMap<String, String> identityHashMap =
            new IdentityHashMap<>();

        identityHashMap.put("One", "Un");
        identityHashMap.put("Two", "Deux");
        identityHashMap.put("Three", "Trois");

        Set<Map.Entry<String, String>> entrySet = identityHashMap.entrySet();
        HashSet<Map.Entry<String, String>> hashSet = new HashSet<>(entrySet);

        // NB: These comparisons are valid in this case because none of the
        //     keys put into 'identityHashMap' above are equal to any other.
        if (false == hashSet.equals(entrySet)) {
            throw new RuntimeException("Test FAILED: Sets are not equal.");
        }
        if (hashSet.hashCode() != entrySet.hashCode()) {
            throw new RuntimeException("Test FAILED: Set's hashcodes are not equal.");
        }
    }
}