diff -r 73da889306b7 -r f46bfa7a2956 src/demo/share/jfc/SwingSet2/Permuter.java --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/demo/share/jfc/SwingSet2/Permuter.java Fri Mar 23 13:43:39 2018 -0700 @@ -0,0 +1,110 @@ +/* + * + * Copyright (c) 2007, Oracle and/or its affiliates. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * - Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * - Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * - Neither the name of Oracle nor the names of its + * contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS + * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, + * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR + * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR + * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, + * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, + * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR + * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF + * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING + * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS + * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + + + +import java.util.Random; + +/** + * An object that implements a cheesy pseudorandom permutation of the integers + * from zero to some user-specified value. (The permutation is a linear + * function.) + * + * @author Josh Bloch + */ +class Permuter { + /** + * The size of the permutation. + */ + private int modulus; + + /** + * Nonnegative integer less than n that is relatively prime to m. + */ + private int multiplier; + + /** + * Pseudorandom nonnegative integer less than n. + */ + private int addend = 22; + + public Permuter(int n) { + if (n<0) { + throw new IllegalArgumentException(); + } + modulus = n; + if (n==1) { + return; + } + + // Initialize the multiplier and offset + multiplier = (int) Math.sqrt(n); + while (gcd(multiplier, n) != 1) { + if (++multiplier == n) { + multiplier = 1; + } + } + } + + /** + * Returns the integer to which this permuter maps the specified integer. + * The specified integer must be between 0 and n-1, and the returned + * integer will be as well. + */ + public int map(int i) { + return (multiplier * i + addend) % modulus; + } + + /** + * Calculate GCD of a and b, which are assumed to be non-negative. + */ + private static int gcd(int a, int b) { + while(b != 0) { + int tmp = a % b; + a = b; + b = tmp; + } + return a; + } + + /** + * Simple test. Takes modulus on command line and prints out permutation. + */ + public static void main(String[] args) { + int modulus = Integer.parseInt(args[0]); + Permuter p = new Permuter(modulus); + for (int i=0; i