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Rooted by: Trollderim's Kumite #1
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  • Code 
    public class Primes {
  public static boolean isAPrime(int number) {    
    if (number == 1) {
      return false;
    }
  
    if (number == 2) {
      return true;
    }
    
    if (number % 2 == 0) {
      return false;
    }
  
    for (int i = 3; i*i <= number; i += 2) {
      if (number % i == 0)
        return false;
    }
    
    return true;
  }
}
     Test Cases 
    import org.junit.Test;
import static org.junit.Assert.assertEquals;
import org.junit.runners.JUnit4;
import java.util.Random;

public class SolutionTest {
    private static final Random RANDOM = new Random();

    @Test
    public void twoShouldBeAPrime() {
      testPrime(2, true);
    }

    @Test
    public void fourShouldNotBeAPrime() {
      testPrime(4, false);
    }
    
    @Test
    public void aSquareShouldNotAPrime() {
      for (int i = 0; i < 10000; ++i) {
        int randomNumber = RANDOM.nextInt(Short.MAX_VALUE) + 2;
        int numberToCheck = randomNumber * randomNumber;
        testPrime(numberToCheck, false);
      }
    }
    
    @Test
    public void aProductOfTwoIntegersShouldNotBeAPrime() {
      for (int i = 0; i < 100000; ++i) {
        int a = RANDOM.nextInt(Short.MAX_VALUE) + 2;
        int b = RANDOM.nextInt(Short.MAX_VALUE) + 2;
        int numberToCheck = a * b;
        testPrime(numberToCheck, false);
      }
    }
    
    private static void testPrime(int numberToCheck, boolean expected) {     
      boolean actual = Primes.isAPrime(numberToCheck);
      assertEquals(Integer.toString(numberToCheck), expected, actual);
    }
}
    View Run Output
  • Code
    • public class Primes {
    • public static boolean isAPrime(int number) {
    • for (int i=2;i*i<=number;i++)
    • {
    • public static boolean isAPrime(int number) {
    • if (number == 1) {
    • return false;
    • }
    • if (number == 2) {
    • return true;
    • }
    • if (number % 2 == 0) {
    • return false;
    • }
    • for (int i = 3; i*i <= number; i += 2) {
    • if (number % i == 0)
    • return false;
    • }
    • return true;
    • }
    • }
     Test Cases
    • import org.junit.Test;
    • import static org.junit.Assert.assertEquals;
    • import org.junit.runners.JUnit4;
    • import java.util.Random;
    • public class SolutionTest {
    • private static final Random RANDOM = new Random();
    • @Test
    • public void twoShouldBeAPrime() {
    • int numberToCheck = 2;
    • boolean expected = true;
    • testPrime(2, true);
    • }
    • @Test
    • public void fourShouldNotBeAPrime() {
    • testPrime(4, false);
    • }
    • @Test
    • public void aSquareShouldNotAPrime() {
    • for (int i = 0; i < 10000; ++i) {
    • int randomNumber = RANDOM.nextInt(Short.MAX_VALUE) + 2;
    • int numberToCheck = randomNumber * randomNumber;
    • testPrime(numberToCheck, false);
    • }
    • }
    • @Test
    • public void aProductOfTwoIntegersShouldNotBeAPrime() {
    • for (int i = 0; i < 100000; ++i) {
    • int a = RANDOM.nextInt(Short.MAX_VALUE) + 2;
    • int b = RANDOM.nextInt(Short.MAX_VALUE) + 2;
    • int numberToCheck = a * b;
    • testPrime(numberToCheck, false);
    • }
    • }
    • private static void testPrime(int numberToCheck, boolean expected) {
    • boolean actual = Primes.isAPrime(numberToCheck);
    • assertEquals(expected, actual);
    • assertEquals(Integer.toString(numberToCheck), expected, actual);
    • }
    • }