org.eurekaclinical.i2b2.client.CustomNullHashMap Maven / Gradle / Ivy

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package org.eurekaclinical.i2b2.client;

/*
 * #%L
 * i2b2 Export Service
 * %%
 * Copyright (C) 2013 Emory University
 * %%
 * 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.
 * #L%
 */
import java.util.HashMap;

/**
 * A hash map that will return a specified value if a key is not in the map.
 *
 * @param  the type of the map's keys
 * @param  the type of the map's values
 *
 * @author Michel Mansour
 * @since 1.0
 */
class CustomNullHashMap extends HashMap {

    private static final long serialVersionUID = 1L;

    private final V missingKeyValue;

    /**
     * Accepts the value that should be returned if {@link #get(Object)} is
     * called with a key that the map does not contain.
     *
     * @param missingKeyValue the value that {@link #get(Object)} should return
     * if a key is not in the map
     */
    CustomNullHashMap(V missingKeyValue) {
        super();
        this.missingKeyValue = missingKeyValue;
    }

    /**
     * Default constructor. Sets the missing value to null.
     */
    CustomNullHashMap() {
        this(null);
    }

    @Override
    public V get(Object key) {
        if (containsKey(key)) {
            return super.get(key);
        } else {
            return missingKeyValue;
        }
    }
}