LinearCongruentialGenerator.java

package com.thealgorithms.others;

/**
 * *
 * A pseudorandom number generator.
 *
 * @author Tobias Carryer
 * @date October 10, 2017
 */
public class LinearCongruentialGenerator {

 private final double a;
 private final double c;
 private final double m;
 private double previousValue;

 /**
 * *
 * These parameters are saved and used when nextNumber() is called. The
 * current timestamp in milliseconds is used as the seed.
 *
 * @param multiplier
 * @param increment
 * @param modulo The maximum number that can be generated (exclusive). A
 * common value is 2^32.
 */
 public LinearCongruentialGenerator(double multiplier, double increment, double modulo) {
 this(System.currentTimeMillis(), multiplier, increment, modulo);
 }

 /**
 * *
 * These parameters are saved and used when nextNumber() is called.
 *
 * @param seed
 * @param multiplier
 * @param increment
 * @param modulo The maximum number that can be generated (exclusive). A
 * common value is 2^32.
 */
 public LinearCongruentialGenerator(double seed, double multiplier, double increment, double modulo) {
 this.previousValue = seed;
 this.a = multiplier;
 this.c = increment;
 this.m = modulo;
 }

 /**
 * The smallest number that can be generated is zero. The largest number
 * that can be generated is modulo-1. modulo is set in the constructor.
 *
 * @return a pseudorandom number.
 */
 public double nextNumber() {
 previousValue = (a * previousValue + c) % m;
 return previousValue;
 }

 public static void main(String[] args) {
 // Show the LCG in action.
 // Decisive proof that the LCG works could be made by adding each number
 // generated to a Set while checking for duplicates.
 LinearCongruentialGenerator lcg = new LinearCongruentialGenerator(1664525, 1013904223, Math.pow(2.0, 32.0));
 for (int i = 0; i < 512; i++) {
 System.out.println(lcg.nextNumber());
 }
 }
}