first commit

java/expression/OverflowException.java

@@ -0,0 +1,10 @@
+package expression;
+
+/**
+ * @author Doschennikov Nikita (me@fymio.us)
+ */
+public class OverflowException extends ArithmeticException {
+    public OverflowException(String operation) {
+        super("overflow in " + operation);
+    }
+}