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'databene commons' is an open source Java library by Volker Bergmann. It provides extensions to the Java core library by utility classes, abstract concepts and concrete implementations.

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/*
 * Copyright (C) 2004-2015 Volker Bergmann ([email protected]).
 * All rights reserved.
 *
 * Licensed 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.databene.commons.accessor;

import org.databene.commons.Accessor;
import org.databene.commons.NullSafeComparator;

import java.util.Map;

/**
 * Accesses Values from a Map.
 * Created: 11.03.2006 12:39:07
 * @param  the object type to access
 * @param  the key type
 * @param  the the value type
 * @author Volker Bergmann
 */
public class MapAccessor, K, V> implements Accessor {

    /**
     * the key of the object to look up; null is supported.
     */
    private K key;

    public MapAccessor(K key) {
        this.key = key;
    }
    
    // Accessor interface ----------------------------------------------------------------------------------------------

    @Override
	public V getValue(C item) {
        return item.get(key);
    }
    
    // java.lang.Object overrides --------------------------------------------------------------------------------------

    @SuppressWarnings("rawtypes")
    @Override
    public boolean equals(Object o) {
        if (this == o)
            return true;
        if (o == null || getClass() != o.getClass())
            return false;
        final MapAccessor that = (MapAccessor) o;
        return NullSafeComparator.equals(this.key, that.key);
    }

    @Override
    public int hashCode() {
        return (key != null ? key.hashCode() : 0);
    }
}