Quelle OverrideIsEmpty.java Sprache: JAVA

/*
* Copyright (c) 2013, 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.
*
* 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.
*/

/*
* Portions Copyright (c) 2013 IBM Corporation
*/

/**
* @test
* @bug 8019381
* @summary Verify that we do not get exception when we override isEmpty()
*          in a subclass of HashMap
* @author zhangshj@linux.vnet.ibm.com
*/

import java.util.function.BiFunction;
import java.util.HashMap;

public class OverrideIsEmpty {
    public static class NotEmptyHashMap<K,V> extends HashMap<K,V> {
        private K alwaysExistingKey;
        private V alwaysExistingValue;

        @Override
        public V get(Object key) {
            if (key == alwaysExistingKey) {
                return alwaysExistingValue;
            }
            return super.get(key);
        }

        @Override
        public int size() {
            return super.size() + 1;
        }

        @Override
        public boolean isEmpty() {
            return size() == 0;
        }
    }

    public static void main(String[] args) {
        NotEmptyHashMap<Object, Object> map = new NotEmptyHashMap<>();
        Object key = new Object();
        Object value = new Object();
        map.get(key);
        map.remove(key);
        map.replace(key, value, null);
        map.replace(key, value);
        map.computeIfPresent(key, new BiFunction<Object, Object, Object>() {
            public Object apply(Object key, Object oldValue) {
                return oldValue;
            }
        });
    }
}

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