Java Collection Element Get getCardinalityMap(final Collection col)

Description

Returns a Map mapping each unique element in the given Collection to an Integer representing the number of occurances of that element in the Collection .

License

Apache License

Declaration

public static Map getCardinalityMap(final Collection col) 

Method Source Code

//package com.java2s;
//License from project: Apache License 

import java.util.*;

public class Main {
    /**//from  w w  w. ja  v a2s  .  com
     * Returns a {@link Map} mapping each unique element in
     * the given {@link Collection} to an {@link Integer}
     * representing the number of occurances of that element
     * in the {@link Collection}.
     * An entry that maps to <tt>null</tt> indicates that the
     * element does not appear in the given {@link Collection}.
     */
    public static Map getCardinalityMap(final Collection col) {
        HashMap count = new HashMap();
        Iterator it = col.iterator();
        while (it.hasNext()) {
            Object obj = it.next();
            Integer c = (Integer) (count.get(obj));
            if (null == c) {
                count.put(obj, new Integer(1));
            } else {
                count.put(obj, new Integer(c.intValue() + 1));
            }
        }
        return count;
    }
}

Related

1. getAt(Collection col, int index)
2. getAuthzNameFromEntityName(String entityName, Collection authzProvidersNames)
3. getByIndex(Collection