Java Random randomRange(int end)

Description

random Range

License

Open Source License

Declaration

public static int[] randomRange(int end) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.util.*;

public class Main {
    public static int[] randomRange(int end) {
        return randomRange(end, System.currentTimeMillis());
    }/*w  w  w . j av a  2s .  c o m*/

    public static int[] randomRange(int end, long seed) {
        int[] ary = range(end);
        return shuffle(ary, seed);
    }

    public static int[] range(int end) {
        assert end > 0;
        int[] ary = new int[end];
        for (int i = 0; i < end; ++i) {
            ary[i] = i;
        }
        return ary;
    }

    public static int[] range(int start, int end) {
        int l = end - start;
        assert l > 0;
        int[] ary = new int[l];
        for (int i = 0; i < l; ++i) {
            ary[i] = i + start;
        }
        return ary;
    }

    /**
     * 
     * shuffle
     * @param ary
     * @return
     */
    public static int[] shuffle(int[] ary) {
        return shuffle(0, ary, System.currentTimeMillis());
    }

    /**
     * 
     * shuffle
     *
     * @param start start iundex, which is included. 
     * @param ary
     * @return
     */
    public static int[] shuffle(int start, int[] ary) {
        return shuffle(start, ary, System.currentTimeMillis());
    }

    /**
     * random shuffle inspired by libsvm code
     * @param ary
     * @param seed
     * @return
     */
    public static int[] shuffle(int[] ary, long seed) {
        return shuffle(0, ary, seed);
    }

    /**
     * random shuffle inspired by libsvm code
     * 
     * return new int[] instance.
     * 
     * @param start start index, it is processed.
     * @param ary
     * @param seed
     * @return
     */
    public static int[] shuffle(int start, int[] ary, long seed) {
        assert start >= 0 && start < ary.length;
        int len = ary.length;
        // random shuffle
        Random rand = new Random(seed);

        int[] retary = new int[len];
        System.arraycopy(ary, 0, retary, 0, len);
        for (int i = start; i < len; i++) {
            int j = i + (int) (rand.nextDouble() * (len - i));
            int _ = retary[i];
            retary[i] = retary[j];
            retary[j] = _;
        }
        return retary;
    }
}

Related

1. randomPermutation(int size)
2. randomPermutations(int[] tab, Random r)
3. randomPermute(List l, Random rand)
4. randomProbability(double probability)
5. randomPseudo()
6. randomScalingFactor()
7. randomSeed()
8. randomShort()
9. randomSign()