58 lines
1.9 KiB
Java
58 lines
1.9 KiB
Java
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/***
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* A pseudorandom number generator.
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*
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* @author Tobias Carryer
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* Date: October 10, 2017
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*/
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public class LinearCongruentialGenerator {
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private double a, c, m, previousValue;
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/***
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* These parameters are saved and used when nextNumber() is called.
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* The current timestamp in milliseconds is used as the seed.
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*
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* @param multiplier
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* @param increment
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* @param modulo The maximum number that can be generated (exclusive). A common value is 2^32.
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*/
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public LinearCongruentialGenerator( double multiplier, double increment, double modulo ) {
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this(System.currentTimeMillis(), multiplier, increment, modulo);
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}
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/***
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* These parameters are saved and used when nextNumber() is called.
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*
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* @param seed
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* @param multiplier
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* @param increment
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* @param modulo The maximum number that can be generated (exclusive). A common value is 2^32.
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*/
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public LinearCongruentialGenerator( double seed, double multiplier, double increment, double modulo ) {
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this.previousValue = seed;
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this.a = multiplier;
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this.c = increment;
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this.m = modulo;
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}
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/**
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* The smallest number that can be generated is zero.
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* The largest number that can be generated is modulo-1. modulo is set in the constructor.
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* @return a pseudorandom number.
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*/
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public double nextNumber() {
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previousValue = (a * previousValue + c) % m;
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return previousValue;
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}
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public static void main( String[] args ) {
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// Show the LCG in action.
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// Decisive proof that the LCG works could be made by adding each number
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// generated to a Set while checking for duplicates.
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LinearCongruentialGenerator lcg = new LinearCongruentialGenerator(1664525, 1013904223, Math.pow(2.0, 32.0));
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for( int i = 0; i < 512; i++ ) {
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System.out.println(lcg.nextNumber());
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}
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}
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}
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