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76 lines (68 loc) · 2.07 KB
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//--------------------------------------------
// version 3: break, add to list
import java.util.ArrayList;
import java.util.Scanner;
//version 1
public class Primes {
public static void main(String[] args) {
int max = 100;
System.out.println("Prime numbers less than 100:");
for (int x = 2; x <= max; x++) {
if (isPrime(x))
System.out.print(" " + x);
}
System.out.println();
System.out.println("Check a number: ");
Scanner in = new Scanner(System.in);
int num = in.nextInt();
if (isPrime(num))
System.out.println("prime:" + num);
}
public static boolean isPrime(int number)
{
boolean isPrime = true;
if ((number == 0) | (number == 1))
{
isPrime = false;
}
else
{
for(int divisor = 2; divisor < number; divisor++) {
if (number % divisor == 0) {
isPrime = false;
}
}
}
return isPrime;
}
}
/*
* //-------------------------------------------- //version 2: break public
* class Primes2 {
*
* public static void main(String[] args) { int max = 10; for (int x = 2; x <=
* max; x++) { boolean isPrime = true; for (int y = 2; y < x; y++) if (x % y ==
* 0) { isPrime = false; break; } if (isPrime) System.out.println(x); } } }
*
*
* public class Primes3 {
*
* public static void main(String[] args) { ArrayList<Integer> primeList = new
* ArrayList<>();
*
* int max = 10000; for (int x = 2; x <= max; x++) { boolean isPrime = true; for
* (int y = 2; y < x; y++) if (x % y == 0) { isPrime = false; break; } if
* (isPrime) primeList.add(x); } System.out.println(primeList); } }
* //-------------------------------------------- // version 4: break, add to
* list, square root
*
*
* public class Primes4 {
*
* public static void main(String[] args) { ArrayList<Integer> primeList = new
* ArrayList<>();
*
* int max = 200000; for (int x = 2; x <= max; x++) { boolean isPrime = true;
* for (int y = 2; y < Math.sqrt(x); y++) if (x % y == 0) { isPrime = false;
* break; } if (isPrime) primeList.add(x); } System.out.println(primeList); } }
*/