OneUniverse.java

/*
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 * 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.
 *
 * 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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 */

/*
 * @test
 * @bug     6276988
 * @summary All enum constants in a class should share a single "universe".
 * @modules java.base/java.util:open
 */

import java.lang.reflect.Field;
import java.math.RoundingMode;
import java.util.EnumSet;

public class OneUniverse {

    private static final Field universeField;

    static {
        try {
            universeField = EnumSet.class.getDeclaredField("universe");
        } catch (NoSuchFieldException e) {
            throw new AssertionError(e);
        }
        universeField.setAccessible(true);
    }

    public static void main(String... args) {

        EnumSet<RoundingMode> noneSet = EnumSet.noneOf(RoundingMode.class);
        EnumSet<RoundingMode> allSet  = EnumSet.allOf(RoundingMode.class);

        if (getUniverse(noneSet) != getUniverse(allSet)) {
            throw new AssertionError(
                    "Multiple universes detected.  Inform the bridge!");
        }
    }

    private static <E extends Enum<E>> Enum<E>[] getUniverse(EnumSet<E> set) {
        try {
            return (Enum<E>[]) universeField.get(set);
        } catch (IllegalAccessException e) {
            throw new AssertionError(e);
        }
    }
}