add all variants for 'Sum' task (hw2)

java/sum/SumDouble.java

@@ -0,0 +1,23 @@
+package sum;
+
+/**
+ * @author Nikita Doschennikov (me@fymio.us)
+ */
+public class SumDouble {
+    public static void main(String[] args) {
+        double res = 0.0; // 0_0
+        for (String arg : args) {
+            StringBuilder builder = new StringBuilder();
+            for (char c : arg.toCharArray()) {
+                if (!Character.isWhitespace(c)) {
+                    builder.append(c);
+                } else {
+                    res += (!builder.toString().isEmpty()) ? Double.parseDouble(builder.toString()) : 0;
+                    builder = new StringBuilder();
+                }
+            }
+            res += (!builder.toString().isEmpty()) ? Double.parseDouble(builder.toString()) : 0;
+        }
+        System.out.println(res);
+    }
+}