Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.util.ArrayList;

import java.util.Iterator;
import java.util.List;
import java.util.Map;

public class Main {
    /**
     * Returns a List of Lists: all combinations of the elements of the given
     * List.
     *
     * @param maxCombinationSize combinations larger than this value are
     * discarded
     */
    public static List combinations(List original, int maxCombinationSize) {
        return combinations(original, maxCombinationSize, null);
    }

    /**
     * Returns a List of Lists: all combinations of the elements of the given
     * List.
     *
     * @param maxCombinationSize combinations larger than this value are
     * discarded
     * @param mandatoryItem an item that all returned combinations must contain,
     * or null to leave unspecified
     */
    public static List combinations(List original, int maxCombinationSize, Object mandatoryItem) {
        ArrayList combinations = new ArrayList();

        //Combinations are given by the bits of each binary number from 1 to 2^N
        for (int i = 1; i <= ((int) Math.pow(2, original.size()) - 1); i++) {
            ArrayList combination = new ArrayList();
            for (int j = 0; j < original.size(); j++) {
                if ((i & (int) Math.pow(2, j)) > 0) {
                    combination.add(original.get(j));
                }
            }
            if (combination.size() > maxCombinationSize) {
                continue;
            }
            if ((mandatoryItem != null) && !combination.contains(mandatoryItem)) {
                continue;
            }
            combinations.add(combination);
        }

        return combinations;
    }

    /**
     * Returns a List of Lists: all combinations of the elements of the given
     * List.
     */
    public static List combinations(List original) {
        return combinations(original, original.size(), null);
    }

    public static Object get(Class c, Map map) {
        if (map.keySet().contains(c)) {
            return map.get(c);
        }
        for (Iterator i = map.keySet().iterator(); i.hasNext();) {
            Class candidateClass = (Class) i.next();
            if (candidateClass.isAssignableFrom(c)) {
                return map.get(candidateClass);
            }
        }

        return null;
    }
}