BAEL-4503

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/Calculator.java

@@ -0,0 +1,37 @@
+package com.baeldung.constantspatterns;
+
+public class Calculator {
+    public static final double PI = 3.14159265359;
+    private static final double UPPER_LIMIT = 0x1.fffffffffffffP+1023;
+
+    public enum Operation {
+        ADD, SUBTRACT, DIVIDE, MULTIPLY
+    }
+
+    public double operateOnTwoNumbers(double numberOne, double numberTwo, Operation operation) {
+        if (numberOne > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberOne' is too large");
+        }
+        if (numberTwo > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberTwo' is too large");
+        }
+        double answer = 0;
+
+        switch (operation) {
+        case ADD:
+            answer = numberOne + numberTwo;
+            break;
+        case SUBTRACT:
+            answer = numberOne - numberTwo;
+            break;
+        case DIVIDE:
+            answer = numberOne / numberTwo;
+            break;
+        case MULTIPLY:
+            answer = numberOne * numberTwo;
+            break;
+        }
+
+        return answer;
+    }
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/CalculatorConstants.java

@@ -0,0 +1,10 @@
+package com.baeldung.constantspatterns;
+
+public interface CalculatorConstants {
+    double PI = 3.14159265359;
+    double UPPER_LIMIT = 0x1.fffffffffffffP+1023;
+
+    enum Operation {
+        ADD, SUBTRACT, MULTIPLY, DIVIDE
+    };
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/GeometryCalculator.java

@@ -0,0 +1,32 @@
+package com.baeldung.constantspatterns;
+
+public class GeometryCalculator implements CalculatorConstants {
+    public static final double UPPER_LIMIT = 100000000000000000000.0;
+
+    public double operateOnTwoNumbers(double numberOne, double numberTwo, Operation operation) {
+        if (numberOne > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberOne' is too large");
+        }
+        if (numberTwo > UPPER_LIMIT) {
+            throw new IllegalArgumentException("'numberTwo' is too large");
+        }
+        double answer = 0;
+
+        switch (operation) {
+        case ADD:
+            answer = numberOne + numberTwo;
+            break;
+        case SUBTRACT:
+            answer = numberOne - numberTwo;
+            break;
+        case DIVIDE:
+            answer = numberOne / numberTwo;
+            break;
+        case MULTIPLY:
+            answer = numberOne * numberTwo;
+            break;
+        }
+
+        return answer;
+    }
+}

core-java-modules/core-java-lang-3/src/main/java/com/baeldung/constantspatterns/calculations/MathConstants.java

@@ -0,0 +1,16 @@
+package com.baeldung.constantspatterns.calculations;
+
+public final class MathConstants {
+    public static final double PI = 3.14159265359;
+    public static final double GOLDEN_RATIO = 1.6180;
+    public static final double GRAVITATIONAL_ACCELERATION = 9.8;
+    public static final double EULERS_NUMBER = 2.7182818284590452353602874713527;
+
+    public enum Operation {
+        ADD, SUBTRACT, DIVIDE, MULTIPLY
+    }
+
+    private MathConstants() {
+
+    }
+}

core-java-modules/core-java-lang-3/src/test/java/com/baeldung/constantspatterns/ConstantPatternUnitTest.java

@@ -0,0 +1,23 @@
+package com.baeldung.constantspatterns;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.Test;
+
+public class ConstantPatternUnitTest {
+    @Test
+    public void givenTwoNumbersAndAdd_whenCallingCalculatorOperatOneTwoNumbers_correctAnswerReturned() {
+        Calculator calculator = new Calculator();
+        double expected = 4;
+        double answer = calculator.operateOnTwoNumbers(2, 2, Calculator.Operation.ADD);
+        assertEquals(expected, answer);
+    }
+    
+    @Test
+    public void givenTwoNumbersAndAdd_whenCallingGeometryCalculatorOperatOneTwoNumbers_correctAnswerReturned() {
+        GeometryCalculator calculator = new GeometryCalculator();
+        double expected = 4;
+        double answer = calculator.operateOnTwoNumbers(2, 2, GeometryCalculator.Operation.ADD);
+        assertEquals(expected, answer);
+    }
+}