Using Static Initialisation

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

@@ -4,6 +4,25 @@ public class MathEquation {
     private char opCode;
     private double result;
 
+    private static int numOfCalculations;
+    private static double sumOfResults;
+
+    // Empty constructor to allow us to use MathEquation without needing to pass in anything
+    public MathEquation() {}
+
+    // This only exists as a demo for chaining constructors
+    public MathEquation(char opCode) {
+        this.opCode = opCode;
+    }
+
+    // Demonstrating how chaining constructors works
+    public MathEquation(char opCode, double leftVal, double rightVal) {
+        this(opCode);
+        this.leftVal = leftVal;
+        this.rightVal = rightVal;
+    }
+
+    // Method to execute the calculations
     void execute() {
         switch (this.opCode) {
             case 'a':
@@ -23,6 +42,12 @@ public class MathEquation {
                 this.result = 0.0d;
                 break;
         }
+        numOfCalculations++;
+        sumOfResults += result;
+    }
+
+    public static double getAverageResult() {
+        return sumOfResults / numOfCalculations;
     }
 
     public MathEquation(double leftVal, double rightVal, char opCode, double result) {

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

@@ -1,5 +1,3 @@
-import java.util.ArrayList;
-
 public class NewCalcEngine {
 
     public static void main(String[] args) {
@@ -9,24 +7,16 @@ public class NewCalcEngine {
     static void performCalculations() {
 
         MathEquation[] mathEquation = new MathEquation[4];
-        mathEquation[0] = create(100.0d, 50.0d, 'd');
-        mathEquation[1] = create(25.0d, 92.0d, 'a');
-        mathEquation[2] = create(225.0d, 17.0d, 's');
-        mathEquation[3] = create(11.0d, 3.0d, 'm');
+        mathEquation[0] = new MathEquation('d', 100.0d, 50.0d);
+        mathEquation[1] = new MathEquation('a', 25.0d, 92.0d);
+        mathEquation[2] = new MathEquation('s', 225.0d, 17.0d);
+        mathEquation[3] = new MathEquation('m', 11.0d, 3.0d);
 
-        for (MathEquation equation: mathEquation) {
+        for (MathEquation equation : mathEquation) {
             equation.execute();
-            System.out.println("Result = " + equation.result);
+            System.out.println("Result = " + equation.getResult());
         }
-    }
-
-    static MathEquation create(double leftVal, double rightVal, char opCode) {
-        MathEquation mathEquation = new MathEquation();
-        
-        mathEquation.leftVal = leftVal;
-        mathEquation.rightVal = rightVal;
-        mathEquation.opCode = opCode;
 
-        return mathEquation;
+        System.out.println("Average Result = " + MathEquation.getAverageResult());
     }
 }