Main.java Source code

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Here is the source code for Main.java

Source

//package com.java2s;
/**
 * License: src/main/resources/license/escidoc.license
 */

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.LinkedHashSet;
import java.util.Map;
import java.util.Set;

public class Main {
    private static Integer INTEGER_ONE = new Integer(1);

    /**
     * Make INTERSECTION operation between 2 {@link Collection}
     * 
     * @param a
     * @param b
     * @return
     */
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static Collection intersection(final Collection a, final Collection b) {
        ArrayList list = new ArrayList();
        Map mapa = getCardinalityMap(a);
        Map mapb = getCardinalityMap(b);
        Set elts = new LinkedHashSet(a);
        elts.addAll(b);
        Iterator it = elts.iterator();
        while (it.hasNext()) {
            Object obj = it.next();
            for (int i = 0, m = Math.min(getFreq(obj, mapa), getFreq(obj, mapb)); i < m; i++) {
                list.add(obj);
            }
        }
        return list;
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    public static Map getCardinalityMap(final Collection coll) {
        Map count = new HashMap();
        for (Iterator it = coll.iterator(); it.hasNext();) {
            Object obj = it.next();
            Integer c = (Integer) (count.get(obj));
            if (c == null) {
                count.put(obj, INTEGER_ONE);
            } else {
                count.put(obj, new Integer(c.intValue() + 1));
            }
        }
        return count;
    }

    @SuppressWarnings({ "rawtypes" })
    private static final int getFreq(final Object obj, final Map freqMap) {
        Integer count = (Integer) freqMap.get(obj);
        if (count != null) {
            return count.intValue();
        }
        return 0;
    }
}