Demonstrating Custom Interfaces

Java Classes & Interfaces/New Calc Engine/src/MathProcessing.java

@@ -0,0 +1,9 @@
+public interface MathProcessing {
+    
+    String SEPARATOR = " ";
+    String getKeyWord();
+    double doCalculation(double leftVal, double rightVal);
+    default String doFormatting() {
+        return null;
+    }
+}