Question

Write a test client for Randomthat checks that two methods, namely, nextGaussian()and nextLong()in the library operate as expected. Take a command-line argument N, generate Nrandom numbers using each of the methods in Random, and print out their mean, and standard deviation.

Part 2: Implement a class that extends Random with a static method maxwellBoltzmann() that returns a random value drawn from a Maxwell-Boltzmann distribution with parameter s. To produce such a value, return the square root of the sum of the squares of three Gaussian random variables with mean 0 and standard deviation s. The speeds of molecules in an ideal gas have a Maxwell-Boltzmann distribution. Write a test client to test this new method, taking as command-line arguments N and sand prints N random numbers from the Maxwell Boltzmann distribution with parameter s.

Answer 1

/ TestRandom.java

import java.util.Random;

public class TestRandom {

// method to find the mean value of set of numbers

// using Number as data type, so that it can represent both Double and Long

// types needed for this program

static double calculateMean(Number array[]) {

double sum = 0;

// summing values

for (int i = 0; i < array.length; i++) {

sum += array[i].doubleValue();

}

// finding average and returning it

double avg = (double) sum / array.length;

return avg;

}

// method to find the standard deviation value of set of numbers

// using Number as data type, so that it can represent both Double and Long

// types needed for this program

static double calculateSD(Number array[], double mean) {

// initializing sum of squared difference between each number and mean

// to 0

double sumSquaredDiff = 0;

// looping

for (int i = 0; i < array.length; i++) {

// finding difference between current number and mean, squaring the

// result, adding to sumSquaredDiff

sumSquaredDiff += Math.pow(array[i].doubleValue() - mean, 2);

}

// finding variance

double variance = (double) sumSquaredDiff / array.length;

// finding square root of variance as standard deviation

double sd = Math.sqrt(variance);

return sd;

}

public static void main(String[] args) {

// if no command line arguments given, displaying usage and quit

if (args.length == 0) {

System.out.println("Usage: java TestRandom <n>");

System.exit(0);

}

// parsing first argument as integer N

int N = Integer.parseInt(args[0]);

// declaring a Double array and a Long array of size N

Double gaussian[] = new Double[N];

Long lng[] = new Long[N];

// Random number generator

Random random = new Random();

// looping for N times

for (int i = 0; i < N; i++) {

// generating a guassian number, adding to array

gaussian[i] = random.nextGaussian();

// generating a long number, adding to array

lng[i] = random.nextLong();

}

// finding average and standard deviation of both array values, we can

// use the same functions for both types

double avgGaussian = calculateMean(gaussian);

double sdGaussian = calculateSD(gaussian, avgGaussian);

double avgLong = calculateMean(lng);

double sdLong = calculateSD(lng, avgLong);

// displaying mean and standard deviation of both, formatted to 2 digits

// after decimal point. the gaussian values will yeild a mean value

// close to 0 and a standard deviation close to 1

System.out.printf("Mean of %d gaussian values: %.2f\\", N, avgGaussian);

System.out.printf("Standard deviation: %.2f\\", sdGaussian);

System.out.printf("Mean of %d long values: %.2f\\", N, avgLong);

System.out.printf("Standard deviation: %.2f\\", sdLong);

}

}

Step-by-step explanation: