001package hw3.optional;
002
003public class Primes {
004
005    private static void findPrimes(int nValues) {
006        boolean isPrime = true;
007
008        for (int i = 2; i <= nValues; i++) {
009            isPrime = true;
010
011            for (int j = 2; j < i; j++) {
012                if (i % j == 0) {
013                    isPrime = false;
014                    break;
015                }
016            }
017
018            if (isPrime) {
019                System.out.println(i);
020            }
021        }
022    }
023
024
025    private static void findPrimesFaster(int nValues) {
026        // PLACE YOUR IMPLEMENTATION HERE
027        System.out.println("The method findPrimesFaster has not been implemented");
028    }
029
030
031    private static void findPrimesEvenFaster(int nValues) {
032        // PLACE YOUR IMPLEMENTATION HERE
033        System.out.println("The method findPrimesEvenFaster has not been implemented");
034    }
035
036
037
038    public static void main(String[] args) {
039
040        // Find and print all primes between 0 and 50.
041
042        System.out.println("Running method findPrimes:");
043        findPrimes(50);
044
045        System.out.println("\nRunning method findPrimesFaster:");
046        findPrimesFaster(50);
047
048        System.out.println("\nRunning method findPrimesEvenFaster:");
049        findPrimesEvenFaster(50);
050
051
052
053        // Time how long it takes to find primes.
054
055        long startTime = 0;
056        long endTime = 0;
057
058
059        System.out.print("\n\nTiming method findPrimes:");
060        startTime = System.currentTimeMillis();
061        findPrimes(20000);
062        endTime = System.currentTimeMillis();
063        System.out.println("  " + (endTime-startTime) + " milliseconds");
064
065        System.out.print("\nTiming method findPrimesFaster:");
066        startTime = System.currentTimeMillis();
067        findPrimesFaster(20000);
068        endTime = System.currentTimeMillis();
069        System.out.println("  " + (endTime-startTime) + " milliseconds");
070
071        System.out.print("\nTiming method findPrimesEvenFaster:");
072        startTime = System.currentTimeMillis();
073        findPrimesEvenFaster(20000);
074        endTime = System.currentTimeMillis();
075        System.out.println("  " + (endTime-startTime) + " milliseconds");
076
077
078        System.out.print("\n\nTiming method findPrimes:");
079        startTime = System.currentTimeMillis();
080        findPrimes(50000);
081        endTime = System.currentTimeMillis();
082        System.out.println("  " + (endTime-startTime) + " milliseconds");
083
084        System.out.print("\nTiming method findPrimesFaster:");
085        startTime = System.currentTimeMillis();
086        findPrimesFaster(50000);
087        endTime = System.currentTimeMillis();
088        System.out.println("  " + (endTime-startTime) + " milliseconds");
089
090        System.out.print("\nTiming method findPrimesEvenFaster:");
091        startTime = System.currentTimeMillis();
092        findPrimesEvenFaster(50000);
093        endTime = System.currentTimeMillis();
094        System.out.println("  " + (endTime-startTime) + " milliseconds");
095    }
096
097}