Java Collection Hash hashCodeUnordered(Collection collection)

Description

Calculates the hash code for a given collection not including the order of elements.

License

Apache License

Parameter

Parameter	Description
collection	a parameter

Declaration

public static <E> int hashCodeUnordered(Collection<E> collection) 

Method Source Code

//package com.java2s;
/*******************************************************************************
 * Copyright 2011 Danny Kunz/*  w w w  .ja  v  a 2  s.  co  m*/
 * 
 * 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.
 ******************************************************************************/

import java.util.Collection;
import java.util.Iterator;

public class Main {
    /**
     * Calculates the hash code for a given collection not including the order of elements. This can be used for {@link Set}
     * implementations e.g.
     * 
     * @param collection
     * @return
     */
    public static <E> int hashCodeUnordered(Collection<E> collection) {
        int result = 1;
        if (collection != null) {
            Iterator<E> iterator = collection.iterator();
            while (iterator.hasNext()) {
                E next = iterator.next();
                result = result * (next != null ? next.hashCode() : 0);
            }
        }
        return result;
    }

    /**
     * Calculates the hash code for a given collection including the order of elements
     * 
     * @param collection
     * @return
     */
    public static <E> int hashCode(Collection<E> collection) {
        final int prime = 31;
        int result = 1;
        if (collection != null) {
            Iterator<E> iterator = collection.iterator();
            while (iterator.hasNext()) {
                E next = iterator.next();
                result = prime * result + (next != null ? next.hashCode() : 0);
            }
        }
        return result;
    }
}

Related

1. hashCode(Collection c)
2. hashCode(Collection collection)
3. hashCode(Collection collection)
4. hashCodeDeep(Collection collection)