sample for BAEL-747 Check if a number is prime in Java (eugenp#1508)

core-java/src/main/java/com/baeldung/primechecker/BigIntegerPrimeChecker.java

@@ -0,0 +1,13 @@
+package com.baeldung.primechecker;
+
+import java.math.BigInteger;
+
+public class BigIntegerPrimeChecker implements PrimeChecker{
+
+    @Override
+    public boolean isPrime(int number) {
+        BigInteger bigInt = BigInteger.valueOf(number);
+        return bigInt.isProbablePrime(100);
+    }
+
+}

core-java/src/main/java/com/baeldung/primechecker/BruteForcePrimeChecker.java

@@ -0,0 +1,13 @@
+package com.baeldung.primechecker;
+
+import java.util.stream.IntStream;
+
+public class BruteForcePrimeChecker implements PrimeChecker{
+
+    @Override
+    public boolean isPrime(int number) {
+        return IntStream.range(2, number).filter(n -> (number % n == 0)).count() == 0;
+    }
+
+
+}       

core-java/src/main/java/com/baeldung/primechecker/OptimisedPrimeChecker.java

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+package com.baeldung.primechecker;
+
+import java.util.stream.IntStream;
+
+public class OptimisedPrimeChecker implements PrimeChecker{
+
+    @Override
+    public boolean isPrime(int number) {
+        return IntStream.range(2, (int)Math.sqrt(number) + 1)
+            .filter(n -> (number % n == 0))
+            .count() == 0;
+    }
+
+
+}

core-java/src/main/java/com/baeldung/primechecker/PrimeChecker.java

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+package com.baeldung.primechecker;
+
+public interface PrimeChecker {
+
+    public boolean isPrime( int number );
+}

core-java/src/main/java/com/baeldung/primechecker/PrimesPrimeChecker.java

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+package com.baeldung.primechecker;
+
+import org.apache.commons.math3.primes.Primes;
+
+public class PrimesPrimeChecker implements PrimeChecker{
+
+    @Override
+    public boolean isPrime(int number) {
+        return Primes.isPrime(number);
+    }
+
+}

core-java/src/test/java/com/baeldung/primechecker/BigIntegerPrimeCheckerTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.primechecker;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class BigIntegerPrimeCheckerTest {
+
+    PrimeChecker primeChecker = new BigIntegerPrimeChecker();
+
+    @Test
+    public void givenPrimeNumber_whenCheckIsPrime_thenTrue(){
+        assertTrue(primeChecker.isPrime(13));
+        assertTrue(primeChecker.isPrime(1009));
+    }
+
+    @Test
+    public void givenNonPrimeNumber_whenCheckIsPrime_thenFalse(){
+        assertTrue(!primeChecker.isPrime(50));
+        assertTrue(!primeChecker.isPrime(1001));
+    }
+
+}

core-java/src/test/java/com/baeldung/primechecker/BruteForcePrimeCheckerTest.java

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+package com.baeldung.primechecker;
+
+import org.junit.Test;
+import static org.junit.Assert.*;
+
+public class BruteForcePrimeCheckerTest {
+
+    BruteForcePrimeChecker primeChecker = new BruteForcePrimeChecker();
+
+    @Test
+    public void givenPrimeNumber_whenCheckIsPrime_thenTrue(){
+        assertTrue(primeChecker.isPrime(13));
+        assertTrue(primeChecker.isPrime(1009));
+    }
+
+    @Test
+    public void givenNonPrimeNumber_whenCheckIsPrime_thenFalse(){
+        assertTrue(!primeChecker.isPrime(50));
+        assertTrue(!primeChecker.isPrime(1001));
+    }
+
+
+
+}

core-java/src/test/java/com/baeldung/primechecker/OptimisedPrimeCheckerTest.java

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+package com.baeldung.primechecker;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class OptimisedPrimeCheckerTest {
+
+    PrimeChecker primeChecker = new OptimisedPrimeChecker();
+
+    @Test
+    public void givenPrimeNumber_whenCheckIsPrime_thenTrue(){
+        assertTrue(primeChecker.isPrime(13));
+        assertTrue(primeChecker.isPrime(1009));
+    }
+
+    @Test
+    public void givenNonPrimeNumber_whenCheckIsPrime_thenFalse(){
+        assertTrue(!primeChecker.isPrime(50));
+        assertTrue(!primeChecker.isPrime(1001));
+    }
+
+}

core-java/src/test/java/com/baeldung/primechecker/PrimesPrimeCheckerTest.java

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+package com.baeldung.primechecker;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class PrimesPrimeCheckerTest {
+    PrimeChecker primeChecker = new PrimesPrimeChecker();
+
+    @Test
+    public void givenPrimeNumber_whenCheckIsPrime_thenTrue() {
+        assertTrue(primeChecker.isPrime(13));
+        assertTrue(primeChecker.isPrime(1009));
+    }
+
+    @Test
+    public void givenNonPrimeNumber_whenCheckIsPrime_thenFalse() {
+        assertTrue(!primeChecker.isPrime(50));
+        assertTrue(!primeChecker.isPrime(1001));
+    }
+
+}