com.philbeaudoin.quebec.client.utils.GwtRandomShuffler.java Source code

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Here is the source code for com.philbeaudoin.quebec.client.utils.GwtRandomShuffler.java

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/**
 * Copyright 2013 Philippe Beaudoin
 *
 * 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.philbeaudoin.quebec.client.utils;

import java.util.ArrayList;

import com.google.gwt.user.client.Random;
import com.philbeaudoin.quebec.shared.game.state.Shuffler;

/**
 * A Shuffler that uses the standard Java random. Not compatible with GWT.
 */
public class GwtRandomShuffler implements Shuffler {

    /**
     * A Fisher-Yates shuffle inspired from the Java source code, restricted to small ArrayList.
     * @param list The list to shuffle
     * @param seed The seed to use.
     */
    @Override
    public <T> void shuffle(ArrayList<T> list, long seed) {
        int size = list.size();
        for (int i = size; i > 1; i--) {
            swap(list, i - 1, Random.nextInt(i));
        }
    }

    /**
     * Swap two elements from an array list.
     * @param list The list.
     * @param a The index of the first element to swap.
     * @param b The index of the second element to swap.
     */
    private static <T> void swap(ArrayList<T> list, int a, int b) {
        T t = list.get(a);
        list.set(a, list.get(b));
        list.set(b, t);
    }
}