import java.util.Random;

public class RandTest {

	public static void printRandom1(int repeat, int max)  {
		for (int i=0; i<repeat; i++) {
			Random r = new Random();
			System.out.println(r.nextInt(max));
		}
	}
	
	public static void printRandom2(int repeat, int max)  {
		Random r = new Random();
		for (int i=0; i<repeat; i++) {
			System.out.println(r.nextInt(max));
		}
	}

	public static void testRandom1(int repeat)  {
		double total = 0;
		double[] values = new double[repeat];
		for (int i=0; i<repeat; i++) {
			Random r = new Random();
			double d = r.nextDouble();
			total += d;
			values[i] = d;
		}
		printStats(repeat, total, values);		
	}

	
	public static void testRandom2(int repeat)  {
		double total = 0;
		double[] values = new double[repeat];
		Random r = new Random();
		for (int i=0; i<repeat; i++) {
			double d = r.nextDouble();
			total += d;
			values[i] = d;
		}
		printStats(repeat, total, values);		
	}

	public static void testRandom3(int repeat)  {
		double total = 0;
		double[] values = new double[repeat];
		for (int i=0; i<repeat; i++) {
			double d = Math.random();
			total += d;
			values[i] = d;
		}
		printStats(repeat, total, values);		
	}

	public static void printStats(int size, double total, double[] values) {
		double mean =  total/size;
		
		double temp = 0;
		for(double a :values) {
			temp += (mean-a)*(mean-a);
		}
		
		double stddev = Math.sqrt(temp/size);

		System.out.format("Mean: %.3f  STDDEV: %.3f%n", mean, stddev);
	}
	

	public static void main(String[] args) {
		// System.out.println("************** 1 ****************");
		// printRandom1(20, 100);
		// System.out.println("************** 2 ****************");
		// printRandom2(20, 100);

		
		System.out.println();
		
		System.out.println("Test 1: initialisera vid varje slumptal");
		testRandom1(10000);
		System.out.println();
		
		System.out.println("Test 2: initialisera innan all slumpning");
		testRandom2(10000);
		System.out.println();
		
		System.out.println("Test 3: använd Math.random()");
		testRandom3(10000);
		System.out.println();
		
	}

}