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Combinatorial objects stream generators for Java.

There is a newer version: 3.4.0

/**
 * Combinatorics Library 3
 * Copyright 2016 Dmytro Paukov [email protected]
 */
package org.paukov.combinatorics3;


import java.util.*;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 * This generator generates multi-combinations (with repetitions) from specified
 * core set by specified length. Core set and length are specified in the
 * constructor of generator
 * 
 * A k-multicombination or k-combination with repetition of a finite set S is
 * given by a sequence of k not necessarily distinct elements of S, where order
 * is not taken into account.
 * 

 * As an example. Suppose there are 2 types of fruits (apple and orange) at a
 * grocery store, and you want to buy 3 pieces of fruit. You could select
 * 

 * (apple, apple, apple)
 * 
(apple, apple, orange)
 * 
(apple, orange, orange)
 * 
(orange, orange, orange)
 * 
 * 
 * Generate 3-combinations with repetitions of the set (apple, orange).
 * 

 * 

 * 

 * 
 *  * 
 * // Create the initial vector of (apple, orange)
 * ICombinatoricsVector<String> initialVector = Factory.createVector(new String[] {
 * 		"apple", "orange" });
 * 
 * // Create a multi-combination generator to generate 3-combinations of
 * // the initial vector
 * Generator<String> gen = Factory.createMultiCombinationGenerator(initialVector,
 * 		3);
 * 
 * // Print all possible combinations
 * for (ICombinatoricsVector<String> combination : gen) {
 * 	System.out.println(combination);
 * }
 * 
 * 
 * 
 * 
 * 
 * @author Dmytro Paukov
 * @version 3.0
 * @see MultiCombinationIterator
 * @param 
 *            Type of elements in the combination
 */
class MultiCombinationGenerator implements IGenerator> {

    final List originalVector;
    final int combinationLength;


    MultiCombinationGenerator(Collection originalVector,
			int combinationsLength) {
		this.originalVector = new ArrayList<>(originalVector);
		if (combinationsLength < 0)
			combinationLength = 0;
		else
			combinationLength = combinationsLength;
	}


	@Override
	public Iterator> iterator() {
		return new MultiCombinationIterator<>(this);
	}


    @Override
    public Stream> stream() {
        return StreamSupport.stream(Spliterators.spliteratorUnknownSize(iterator(), 0), false);
    }
}