More efficient isPrime() method

Java/Advanced/Prime Checker/Solution.java

@@ -24,15 +24,19 @@ class Prime {
     boolean isPrime(int n) {
         if (n < 2) {
             return false;
+        } else if (n == 2) {     // account for even numbers now, so that we can do i+=2 in loop below
+            return true;
+        } else if (n % 2 == 0) { // account for even numbers now, so that we can do i+=2 in loop below
+            return false;
         }
         int sqrt = (int) Math.sqrt(n);
-        for (int i = 2; i <= sqrt; i++) {
+        for (int i = 3; i <= sqrt; i += 2) { // skips even numbers for faster results
             if (n % i == 0) {
                 return false;
             }
         }
         return true;
-    }   
+    }
 }
 
 public class Solution {

Java/Introduction/Java Date and Time/Solution.java

@@ -6,16 +6,20 @@ import java.util.Scanner;
 import java.time.LocalDate;
 
 public class Solution {
+    public static String getDay(String day, String month, String year) {
+        int d = Integer.valueOf(day);
+        int m = Integer.valueOf(month);
+        int y = Integer.valueOf(year);
+        LocalDate date = LocalDate.of(y, m, d);
+        return date.getDayOfWeek().toString();
+    }
+
     public static void main(String[] args) {
-        /* Read input */
-        Scanner scan = new Scanner(System.in);
-        int month = scan.nextInt();
-        int day   = scan.nextInt();
-        int year  = scan.nextInt();
-        scan.close();
+        Scanner in = new Scanner(System.in);
+        String month = in.next();
+        String day   = in.next();
+        String year  = in.next();
         
-        /* Create LocalDate instance */
-        LocalDate date = LocalDate.of(year, month, day);
-        System.out.println(date.getDayOfWeek());
+        System.out.println(getDay(day, month, year));
     }
 }