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Contains the entire NEBA core implementation, i.e. the framework that interprets the NEBA API annotations and provides implementations for the service and lifecycle callback interfaces provided in the NEBA API. This package must not export anything as its implementation details are entirely private.

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/**
 * Copyright 2013 the original author or authors.
 * 
 * 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 io.neba.core.util;

import java.util.Arrays;

import static org.apache.commons.lang.StringUtils.join;

/**
 * A key based on multiple values, e.g. for use as a key
 * in a {@link java.util.HashMap}.
 * 
 * @author Olaf Otto
 */
public class Key {
    private static final int CONSTANT = 97;
    private static final int NULL_HASH_CODE = "null".hashCode();
    private int hashCode = 29;
    private final Object[] contents;

    public static Key toKey(Object... contents) {
        return new Key(contents);
    }

    /**
     * @param contents can be null and can contain null elements.
     */
    public Key(Object... contents) {
        this.contents = contents;
        if (contents != null && contents.length != 0) {
            for (Object content : contents) {
                hashCode = hashCode * CONSTANT + (content == null ? NULL_HASH_CODE : content.hashCode());
            }
        } else {
            hashCode =  hashCode * CONSTANT + NULL_HASH_CODE;
        }
    }

    @Override
    public int hashCode() {
        return this.hashCode;
    }
    
    @Override
    public boolean equals(Object obj) {
        return obj == this || obj != null && obj.getClass() == getClass() 
        								  && Arrays.equals(this.contents, ((Key) obj).contents);
    }

    @Override
    public String toString() {
        return "Key {" + join(this.contents, ", ") + '}';
    }
}