java primes

primes/java/src/DefaultPrimes.java

@@ -0,0 +1,33 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class DefaultPrimes implements Primes {
+
+    // (will make the code 15% slower)
+    @SuppressWarnings("ForLoopReplaceableByForEach")
+    public List<Integer> primes(int max) {
+        List<Integer> primesList = new ArrayList<>(10000);
+
+        primesList.add(2);
+
+        for (int i = 3; i < max; i++) { //go through all numbers
+            boolean isPrime = true;
+            for (int j = 0; j < primesList.size(); j++) { //test each number
+                int prime = primesList.get(j);
+                if (prime > Math.sqrt(i)) {
+                    break;
+                }
+                if (i % prime == 0) { //i = test number, j = some known prime
+                    isPrime = false;
+                    break;
+                }
+            }
+
+            if (isPrime) {
+                primesList.add(i);
+            }
+        }
+
+        return primesList;
+    }
+}