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 . - Android java.util

Android examples for java.util:Collection Filter

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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 .

Demo Code

/*/*from www  . j a va2 s. c  o m*/
 * Copyright 1999-2004 The Apache Software Foundation
 *
 * 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 com.java2s;

import java.util.Collection;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

public class Main {
    /**
     * 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;
    }
}

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