add java decision

add java decision

sum.java

@@ -0,0 +1,20 @@
+public class Main {
+
+  public static void main(String[] args) {
+    long start = System.currentTimeMillis();
+    long number = 1_000_000_000;
+    long result = 0;
+
+    for (int i = 0; i < number; i++) {
+      if (i<10){
+        result += i;
+      }else {
+        result = result + (number % 10) + (number/10);
+      }
+    }
+    System.out.println(result);
+    long finish = System.currentTimeMillis();
+    long elapsed = finish - start;
+    System.out.println("Прошло времени, мс: " + elapsed);
+  }
+}