diff --git a/08.Mock/pom.xml b/08.Mock/pom.xml
new file mode 100644
index 0000000..2aaa4a6
--- /dev/null
+++ b/08.Mock/pom.xml
@@ -0,0 +1,31 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <groupId>08</groupId>
+    <artifactId>Mock</artifactId>
+    <version>1.0-SNAPSHOT</version>
+    <dependencies>
+        <dependency>
+            <groupId>org.jetbrains</groupId>
+            <artifactId>annotations-java5</artifactId>
+            <version>15.0</version>
+        </dependency>
+        <dependency>
+            <groupId>junit</groupId>
+            <artifactId>junit</artifactId>
+            <version>4.12</version>
+        </dependency>
+        <dependency>
+            <groupId>org.mockito</groupId>
+            <artifactId>mockito-all</artifactId>
+            <version>1.8.4</version>
+            <scope>test</scope>
+        </dependency>
+
+    </dependencies>
+
+
+</project>
\ No newline at end of file
diff --git a/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Calculator.java b/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Calculator.java
new file mode 100644
index 0000000..d49454c
--- /dev/null
+++ b/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Calculator.java
@@ -0,0 +1,165 @@
+package ru.spbau.mit.alyokhina;
+
+
+import org.jetbrains.annotations.NotNull;
+
+/** By arithmetic expression receives a reverse Polish notation and computes the value */
+public class Calculator {
+    public static void main(String[] argv) {
+        if (argv.length == 0) {
+            System.out.println("Expected expression");
+        } else {
+            Stack<String> expr = new Stack<String>();
+            for (int i = argv[0].length() - 1; i >= 0; i--) {
+                if ((argv[0].charAt(i) >= '0' && argv[0].charAt(i) <= '9') || (argv[0].charAt(i) == '.')) {
+                    StringBuilder sb = new StringBuilder();
+                    while (i < argv[0].length() && ((argv[0].charAt(i) >= '0' && argv[0].charAt(i) <= '9') || (argv[0].charAt(i) == '.'))) {
+                        sb.insert(0, argv[0].charAt(i));
+                        i--;
+                    }
+                    i++;
+                    expr.push(sb.toString());
+                } else if (argv[0].charAt(i) == '+' || argv[0].charAt(i) == '-' || argv[0].charAt(i) == '*' ||
+                        argv[0].charAt(i) == '/' || argv[0].charAt(i) == '(' || argv[0].charAt(i) == ')') {
+                    expr.push(argv[0].substring(i, i + 1));
+                }
+            }
+            Calculator calculator = new Calculator(expr);
+            System.out.println(calculator.getRPN());
+            System.out.println(calculator.calculate());
+        }
+    }
+    /** Stack for storing the expression */
+    private Stack<String> expression = new Stack<String>();
+
+    /** Stack for storing current operands */
+    private Stack<String> operand = new Stack<String>();
+
+    /** Stack for storing reverse Polish notation */
+    private Stack<String> rpn = new Stack<String>();
+
+    /**
+     * Constructor
+     * @param newExpression an expression that needs to be translated into a reverse Polish notation
+     */
+    public Calculator(@NotNull Stack<String> newExpression) {
+        expression = newExpression;
+        rpn = new Stack<String>();
+        operand = new Stack<String>();
+    }
+
+    /**
+     * Constructor
+     * @param newExpression an expression that needs to be translated into a reverse Polish notation
+     * @param forOperand stack for storing the operands
+     * @param forRPN stack for storing reverse Polish notation
+     */
+    public Calculator(@NotNull Stack<String> newExpression, @NotNull Stack<String> forOperand, @NotNull Stack<String> forRPN) {
+        expression = newExpression;
+        rpn = forRPN;
+        operand = forOperand;
+    }
+
+    /**
+     * Get reverse Polish notation
+     * @return reverse Polish notation as a string. All elements are separated by a space. The same value is stored in rpn
+     */
+    public String getRPN() {
+        StringBuilder stringBuilder = new StringBuilder();
+
+        while (!expression.isEmpty()) {
+            String cur = expression.pop();
+            if (cur.equals("(")) {
+                operand.push("(");
+            } else if (cur.equals(")")) {
+                while (!operand.isEmpty() && !operand.peek().equals("(")) {
+                    String str = operand.pop();
+                    rpn.push(str);
+                    stringBuilder.append(" ");
+                    stringBuilder.append(str);
+                }
+                if (!operand.isEmpty()) {
+                    operand.pop();
+                }
+            } else if (isOperand(cur)) {
+                while (!operand.isEmpty() && !operand.peek().equals("(")
+                        && (priority(operand.peek()) >= priority(cur))) {
+                    String str = operand.pop();
+                    rpn.push(str);
+                    stringBuilder.append(" ");
+                    stringBuilder.append(str);
+                }
+                operand.push(cur);
+            } else {
+                rpn.push(cur);
+                stringBuilder.append(" ");
+                stringBuilder.append(cur);
+            }
+        }
+        while (!operand.isEmpty()) {
+            String str = operand.pop();
+            rpn.push(str);
+            stringBuilder.append(" ");
+            stringBuilder.append(str);
+        }
+        return stringBuilder.toString();
+    }
+
+    /**
+     * Calculates the value of the expression
+     * @return The result of calculation of type Double
+     */
+    public Double calculate() {
+        if (!rpn.isEmpty()) {
+            if (isOperand(rpn.peek())) {
+                String op = rpn.pop();
+                return apply(calculate(), calculate(), op);
+            } else {
+                return (Double.parseDouble(rpn.pop()));
+            }
+        } else {
+            return 0.0;
+        }
+    }
+
+    /**
+     * Whether the string is an operand
+     * @param str string, which we want to check
+     * @return true, if this string is operand, else - false
+     */
+    private boolean isOperand(String str) {
+        return (str.equals("+") || str.equals("-") || str.equals("*") || str.equals("/"));
+    }
+
+    /**
+     * Application of operations
+     * @param a,b these values will be applied to the operation
+     * @param op the operation to be applied
+     * @return result of type Double
+     */
+    @NotNull
+    private Double apply(Double a, Double b, String op) {
+        if (op.equals("+")) {
+            return a + b;
+        } else if (op.equals("-")) {
+            return a - b;
+        } else if (op.equals("*")) {
+            return a * b;
+        } else {
+            return a / b;
+        }
+    }
+
+    /**
+     * the priority of an operation
+     * @param operand the operand, the priority of which will be issued
+     * @return priority
+     */
+    private static int priority(@NotNull String operand) {
+        if (operand.equals("+") || operand.equals("-")) {
+            return 1;
+        } else {
+            return 2;
+        }
+    }
+}
diff --git a/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Stack.java b/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Stack.java
new file mode 100644
index 0000000..5e1b70c
--- /dev/null
+++ b/08.Mock/src/main/java/ru/spbau/mit/alyokhina/Stack.java
@@ -0,0 +1,76 @@
+package ru.spbau.mit.alyokhina;
+
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * Stack for Calculator
+ * @param <T> type of stored items
+ */
+public class Stack<T> {
+    /** First element in Stack */
+    Node head = null;
+
+    /**
+     * Add element in Stack
+     * @param newValue element, which will be add
+     */
+    public void push(@NotNull T newValue) {
+        Node newHead = new Node();
+        newHead.value = newValue;
+        newHead.next = head;
+        head = newHead;
+    }
+
+    /**
+     * Delete last added item
+     * @return item that was deleted or null, if there was no such element
+     */
+    public T pop() {
+        if (head != null) {
+            T returnValue = head.value;
+            head = head.next;
+            return returnValue;
+        } else
+            return null;
+    }
+
+    /**
+     * last added item
+     * @return last added item or null if stack is empty
+     */
+    public T peek() {
+        if (head != null)
+            return head.value;
+        else
+            return null;
+    }
+
+    /**
+     * Checking the existence of elements in stack
+     * @return tru, if stack is empty, else - false
+     */
+    public boolean isEmpty() {
+        return (head == null);
+    }
+
+    /**
+     * Moves the stack to a string, separated by a space
+     * @return  resulting string
+     */
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        Node v = head;
+        while (v != null) {
+            sb.append((v.value).toString());
+            sb.append(" ");
+            v = v.next;
+        }
+        return sb.toString();
+    }
+
+    /** Class for Stack. Element of Stack */
+    private class Node {
+        private Node next;
+        private T value;
+    }
+}
diff --git a/08.Mock/src/test/java/ru/spbau/mit/alyokhina/CalculatorTest.java b/08.Mock/src/test/java/ru/spbau/mit/alyokhina/CalculatorTest.java
new file mode 100644
index 0000000..b75df57
--- /dev/null
+++ b/08.Mock/src/test/java/ru/spbau/mit/alyokhina/CalculatorTest.java
@@ -0,0 +1,95 @@
+package ru.spbau.mit.alyokhina;
+
+import org.junit.Test;
+
+import static org.mockito.Mockito.*;
+import static org.junit.Assert.*;
+
+public class CalculatorTest {
+    @Test
+    public void testGetRPN() {
+        Stack<String> expression = mock(Stack.class);
+        Stack<String> operand = mock(Stack.class);
+        Stack<String> rpn = mock(Stack.class);
+        when(expression.isEmpty())
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(true);
+
+        when(expression.pop())
+                .thenReturn("(")
+                .thenReturn("1")
+                .thenReturn("+")
+                .thenReturn("3")
+                .thenReturn(")")
+                .thenReturn("*")
+                .thenReturn("2");
+
+        when(operand.isEmpty())
+                .thenReturn(true)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(true)
+                .thenReturn(false)
+                .thenReturn(true);
+
+        when(operand.peek())
+                .thenReturn("+")
+                .thenReturn("(");
+
+        when(operand.pop())
+                .thenReturn("+")
+                .thenReturn("(")
+                .thenReturn("*");
+
+        Calculator calculator = new Calculator(expression, operand, rpn);
+        assertEquals(" 1 3 + 2 *", calculator.getRPN());
+
+
+        verify(operand).push("(");
+        verify(rpn).push("1");
+        verify(operand).push("+");
+        verify(rpn).push("3");
+        verify(rpn).push("+");
+        verify(operand).push("*");
+        verify(rpn).push("2");
+        verify(rpn).push("*");
+    }
+
+    @Test
+    public void testCalculate() {
+        Stack<String> expression = mock(Stack.class);
+        Stack<String> operand = mock(Stack.class);
+        Stack<String> rpn = mock(Stack.class);
+        when(rpn.isEmpty())
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(false)
+                .thenReturn(true);
+        when(rpn.peek())
+                .thenReturn("*")
+                .thenReturn("2")
+                .thenReturn("+")
+                .thenReturn("3")
+                .thenReturn("1");
+
+        when(rpn.pop())
+                .thenReturn("*")
+                .thenReturn("2")
+                .thenReturn("+")
+                .thenReturn("3")
+                .thenReturn("1");
+        Calculator calculator = new Calculator(expression, operand, rpn);
+        assertEquals((Double) 8.0, calculator.calculate());
+
+    }
+
+}
diff --git a/08.Mock/src/test/java/ru/spbau/mit/alyokhina/StackTest.java b/08.Mock/src/test/java/ru/spbau/mit/alyokhina/StackTest.java
new file mode 100644
index 0000000..b8a5569
--- /dev/null
+++ b/08.Mock/src/test/java/ru/spbau/mit/alyokhina/StackTest.java
@@ -0,0 +1,75 @@
+package ru.spbau.mit.alyokhina;
+
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+public class StackTest {
+    @Test
+    public void testConstructor() {
+        Stack<Integer> s;
+    }
+
+    @Test
+    public void testPush() {
+        Stack<Integer> s = new Stack<Integer>();
+        s.push(3);
+        assertEquals((Integer) 3, s.peek());
+        s.push(5);
+        assertEquals((Integer) 5, s.peek());
+    }
+
+    @Test
+    public void testPopFromEmptyStack() {
+        Stack<Integer> s = new Stack<Integer>();
+        assertEquals(null, s.pop());
+    }
+
+
+    @Test
+    public void testPop() {
+        Stack<Integer> s = new Stack<Integer>();
+        s.push(3);
+        s.push(5);
+        assertEquals((Integer) 5, s.pop());
+        assertEquals((Integer) 3, s.peek());
+    }
+
+    @Test
+    public void testPeekFromEmptyStack() {
+        Stack<Integer> s = new Stack<Integer>();
+        assertEquals(null, s.peek());
+    }
+
+    @Test
+    public void testPeek() {
+        Stack<Integer> s = new Stack<Integer>();
+        s.push(3);
+        s.push(5);
+        assertEquals((Integer) 5, s.peek());
+    }
+
+
+    @Test
+    public void testIsEmptyIfTrue() {
+        Stack<Integer> s = new Stack<Integer>();
+        assertEquals(true, s.isEmpty());
+    }
+
+    @Test
+    public void testIsEmptyIfFalse() {
+        Stack<Integer> s = new Stack<Integer>();
+        s.push(1);
+        assertEquals(false, s.isEmpty());
+    }
+
+    @Test
+    public void print() {
+        Stack<Integer> s = new Stack<Integer>();
+        s.push(3);
+        s.push(5);
+        String t = "5 3 ";
+        assertEquals(t, s.toString());
+    }
+
+}
\ No newline at end of file