added solution

src/main/java/core/basesyntax/Calculator.java

@@ -0,0 +1,5 @@
+package core.basesyntax;
+
+public interface Calculator {
+    double calculate(double a, double b, char ch);
+}

src/main/java/core/basesyntax/CalculatorImpl.java

@@ -0,0 +1,37 @@
+package core.basesyntax;
+
+public class CalculatorImpl implements Calculator {
+    @Override
+    public double calculate(double a, double b, char ch) throws ArithmeticException {
+        double result;
+        switch (ch) {
+            case '+':
+                result = a + b;
+                break;
+            case '-':
+                result = a - b;
+                break;
+            case '*':
+                result = a * b;
+                break;
+            case '/':
+                if (b == 0) {
+                    throw new ArithmeticException();
+                } else {
+                    result = a / b;
+                }
+                break;
+            case '^' :
+                result = Math.pow(a,b);
+                break;
+            default:
+                result = 0;
+        }
+        if (ch != '+' && ch != '-' && ch != '*'
+                && ch != '/' && ch != '^') {
+            throw new IllegalOperationException("This operation is not thought "
+                    + "out for this calculator");
+        }
+        return result;
+    }
+}

src/main/java/core/basesyntax/IllegalOperationException.java

@@ -0,0 +1,8 @@
+package core.basesyntax;
+
+public class IllegalOperationException extends RuntimeException {
+    public IllegalOperationException(String message) {
+        super(message);
+    }
+
+}

src/test/java/core/basesyntax/CalculatorImplTest.java

@@ -0,0 +1,214 @@
+package core.basesyntax;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+class CalculatorImplTest {
+    private static Calculator calculator;
+    private double operand1;
+    private double operand2;
+    private double actual;
+    private char ch;
+
+    @BeforeAll
+    static void beforeAll() {
+        calculator = new CalculatorImpl();
+    }
+
+    @Test
+    void calculate_AdditionTwoPositiveOperands_Ok() {
+        operand1 = 6;
+        operand2 = 7;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+    }
+
+    @Test
+    void calculate_AdditionTwoNegativeOperands_Ok() {
+        operand1 = -6;
+        operand2 = -7;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+    }
+
+    @Test
+    void calculate_AdditionNegativeAndPositiveOperands_Ok() {
+        operand1 = 6;
+        operand2 = -7;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+    }
+
+    @Test
+    void calculate_AdditionZeroDifferentPlaces_Ok() {
+        operand1 = 6;
+        operand2 = 0;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+        operand1 = 0;
+        operand2 = -6;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+    }
+
+    @Test
+    void calculate_AdditionMaxAndMinDoubleValues_Ok() {
+        operand1 = Double.MIN_VALUE;
+        operand2 = Double.MAX_VALUE;
+        ch = '+';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 + operand2,actual);
+    }
+
+    @Test
+    void calculate_SubtractionTwoPositiveOperands_Ok() {
+        operand1 = 6;
+        operand2 = 7;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+    }
+
+    @Test
+    void calculate_SubtractionTwoNegativeOperands_Ok() {
+        operand1 = -6;
+        operand2 = -7;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+    }
+
+    @Test
+    void calculate_SubtractionNegativeAndPositiveOperands_Ok() {
+        operand1 = 6;
+        operand2 = -7;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+    }
+
+    @Test
+    void calculate_SubtractionZeroDifferentPlaces_Ok() {
+        operand1 = 6;
+        operand2 = 0;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+        operand1 = 0;
+        operand2 = -6;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+    }
+
+    @Test
+    void calculate_SubtractionMaxAndMinDoubleValues_Ok() {
+        operand1 = Double.MIN_VALUE;
+        operand2 = Double.MAX_VALUE;
+        ch = '-';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 - operand2,actual);
+    }
+
+    @Test
+    void calculate_MultiplicationTwoPositiveOperands() {
+        operand1 = 5;
+        operand2 = 6;
+        ch = '*';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 * operand2,actual);
+    }
+
+    @Test
+    void calculate_MultiplicationTwoNegativeOperands() {
+        operand1 = -5;
+        operand2 = -6;
+        ch = '*';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 * operand2,actual);
+    }
+
+    @Test
+    void calculate_MultiplicationZeroDifferentPlaces_Ok() {
+        operand1 = 6;
+        operand2 = 0;
+        ch = '*';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(0,actual);
+    }
+
+    @Test
+    void calculate_MultiplicationMaxAndMinDoubleValues_Ok() {
+        operand1 = Double.MIN_VALUE;
+        operand2 = Double.MAX_VALUE;
+        ch = '*';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 * operand2,actual);
+    }
+
+    @Test
+    void calculate_DivisionTwoPositiveOperands() {
+        operand1 = 5;
+        operand2 = 6;
+        ch = '/';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 / operand2,actual);
+    }
+
+    @Test
+    void calculate_DivisionTwoNegativeOperands() {
+        operand1 = -5;
+        operand2 = -6;
+        ch = '/';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 / operand2,actual);
+    }
+
+    @Test
+    void calculate_DivisionZeroDifferentPlaces_Ok() {
+        operand1 = 6;
+        operand2 = 3;
+        ch = '/';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 / operand2,actual);
+        operand2 = 0;
+        assertThrows(ArithmeticException.class, () -> {
+            calculator.calculate(operand1, operand2, ch);
+        });
+    }
+
+    @Test
+    void calculate_DivisionMaxAndMinDoubleValues_Ok() {
+        operand1 = Double.MAX_VALUE;
+        operand2 = Double.MIN_VALUE;
+        ch = '/';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(operand1 / operand2,actual);
+    }
+
+    @Test
+    void calculate_Raising_Ok() {
+        operand1 = 4;
+        operand2 = 5;
+        ch = '^';
+        actual = calculator.calculate(operand1,operand2,ch);
+        assertEquals(Math.pow(operand1,operand2),actual);
+    }
+
+    @Test
+    void calculate_IllegalOperation_NotOk() {
+        if (ch != '+' && ch != '-' && ch != '*' && ch != '/' && ch != '^') {
+            assertThrows(Exception.class, () -> {
+                calculator.calculate(operand1, operand2, ch);
+            });
+        }
+    }
+}