OCP change (#9266)

* OCP change

* calculator unit test

patterns/solid/src/main/java/com/baeldung/o/Addition.java

@@ -0,0 +1,41 @@
+package com.baeldung.o;
+
+public class Addition implements CalculatorOperation {
+    private double number1;
+    private double number2;
+    private double result = 0.0;
+
+    public Addition(double number1, double number2) {
+        this.number1 = number1;
+        this.number2 = number2;
+    }
+
+    public double getNumber1() {
+        return number1;
+    }
+
+    public void setNumber1(double number1) {
+        this.number1 = number1;
+    }
+
+    public double getNumber2() {
+        return number2;
+    }
+
+    public void setNumber2(double number2) {
+        this.number2 = number2;
+    }
+
+    public double getResult() {
+        return result;
+    }
+
+    public void setResult(double result) {
+        this.result = result;
+    }
+
+    @Override
+    public void perform() {
+        result = number1 + number2;
+    }
+}

patterns/solid/src/main/java/com/baeldung/o/Calculator.java

@@ -0,0 +1,14 @@
+package com.baeldung.o;
+
+import java.security.InvalidParameterException;
+
+public class Calculator {
+
+    public void calculate(CalculatorOperation operation) {
+        if (operation == null) {
+            throw new InvalidParameterException("Can not perform operation");
+        }
+
+        operation.perform();
+    }
+}

patterns/solid/src/main/java/com/baeldung/o/CalculatorOperation.java

@@ -0,0 +1,7 @@
+package com.baeldung.o;
+
+public interface CalculatorOperation {
+
+    void perform();
+
+}

patterns/solid/src/main/java/com/baeldung/o/Division.java

@@ -0,0 +1,43 @@
+package com.baeldung.o;
+
+public class Division implements CalculatorOperation {
+    private double number1;
+    private double number2;
+    private double result = 0.0;
+
+    public Division(double number1, double number2) {
+        this.number1 = number1;
+        this.number2 = number2;
+    }
+
+    public double getNumber1() {
+        return number1;
+    }
+
+    public void setNumber1(double number1) {
+        this.number1 = number1;
+    }
+
+    public double getNumber2() {
+        return number2;
+    }
+
+    public void setNumber2(double number2) {
+        this.number2 = number2;
+    }
+
+    public double getResult() {
+        return result;
+    }
+
+    public void setResult(double result) {
+        this.result = result;
+    }
+
+    @Override
+    public void perform() {
+        if (number2 != 0) {
+            result = number1 / number2;
+        }
+    }
+}

patterns/solid/src/main/java/com/baeldung/o/Subtraction.java

@@ -0,0 +1,41 @@
+package com.baeldung.o;
+
+public class Subtraction implements CalculatorOperation {
+    private double number1;
+    private double number2;
+    private double result = 0.0;
+
+    public Subtraction(double number1, double number2) {
+        this.number1 = number1;
+        this.number2 = number2;
+    }
+
+    public double getNumber1() {
+        return number1;
+    }
+
+    public void setNumber1(double number1) {
+        this.number1 = number1;
+    }
+
+    public double getNumber2() {
+        return number2;
+    }
+
+    public void setNumber2(double number2) {
+        this.number2 = number2;
+    }
+
+    public double getResult() {
+        return result;
+    }
+
+    public void setResult(double result) {
+        this.result = result;
+    }
+
+    @Override
+    public void perform() {
+        result = number1 - number2;
+    }
+}

patterns/solid/src/main/test/com/baeldung/o/CalculatorUnitTest.java

@@ -0,0 +1,44 @@
+package com.baeldung.o;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class CalculatorUnitTest {
+
+	private static final double NUMBER_1 = 10.0;
+	private static final double NUMBER_2 = 20.0;
+	private static final double SUM = 30.0;
+	private static final double SUBTRACTION_RESULT = 10.0;
+	private static final double DIVISION_RESULT = 2.0;
+	
+	private Calculator calculator;
+	
+	@BeforeEach
+	public void setUp() {
+		 calculator = new Calculator();
+	}
+
+	@Test
+	public void whenAddTwoNumber_returnSum() {
+		Addition addition = new Addition(NUMBER_1, NUMBER_2);
+		calculator.calculate(addition);
+		assertEquals(SUM, addition.getResult(), 0.0);
+	}
+
+	@Test
+	public void whenSutractTwoNumber_returnCorrectResult() {
+		Subtraction subtraction = new Subtraction(NUMBER_2, NUMBER_1);
+		calculator.calculate(subtraction);
+		assertEquals(SUBTRACTION_RESULT, subtraction.getResult(), 0.0);
+	}
+
+	@Test
+	public void whenDivideTwoNumber_returnCorrectResult() {
+		Division division = new Division(NUMBER_2, NUMBER_1);
+		calculator.calculate(division);
+		assertEquals(DIVISION_RESULT, division.getResult(), 0.0);
+	}
+
+}