diff --git a/Step2/kimyeowon/src/main/java/calculator/Calculator.java b/Step2/kimyeowon/src/main/java/calculator/Calculator.java
new file mode 100644
index 0000000..5c07ee7
--- /dev/null
+++ b/Step2/kimyeowon/src/main/java/calculator/Calculator.java
@@ -0,0 +1,21 @@
+package calculator;
+
+public class Calculator {
+    public int add(int n1, int n2) {
+        return n1 + n2;
+    }
+
+    public int substract(int n1, int n2) {
+        return n1 - n2;
+    }
+
+    public int multiply(int n1, int n2) {
+        return n1 * n2;
+    }
+
+    public int divide(int n1, int n2) {
+        if (n2 == 0) throw new IllegalArgumentException("분모가 0이 될 수 없습니다.");
+        return n1 / n2;
+    }
+
+}
\ No newline at end of file
diff --git a/Step2/kimyeowon/src/main/java/calculator/StringCalculator.java b/Step2/kimyeowon/src/main/java/calculator/StringCalculator.java
new file mode 100644
index 0000000..6954f84
--- /dev/null
+++ b/Step2/kimyeowon/src/main/java/calculator/StringCalculator.java
@@ -0,0 +1,49 @@
+package calculator;
+
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+public class StringCalculator {
+    public int add(String text) {
+        if(isBlank(text)) return 0;
+        return sum(toInts(split(text)));
+    }
+
+    private boolean isBlank(String text) {
+        return text == null || text.isEmpty();
+    }
+
+    private String[] split(String text) {
+        Matcher m = Pattern.compile("//(.)\n(.*)").matcher(text);
+        if(m.find()) {
+            String customDelimeter = m.group(1);
+            return m.group(2).split(customDelimeter);
+        }
+        return text.split(",|:");
+    }
+
+    private int[] toInts(String[] values) {
+        int[] numbers = new int[values.length];
+        for (int i=0; i<numbers.length; i++) {
+            numbers[i] = toPositive(values[i]);
+        }
+        return numbers;
+    }
+
+    private int toPositive(String value) {
+        int number = Integer.parseInt(value);
+        if(number < 0) {
+            throw new RuntimeException();
+        }
+        return number;
+    }
+
+    private int sum(int[] numbers) {
+        int sum = 0;
+        for(int number : numbers) {
+            sum += number;
+        }
+        return sum;
+    }
+
+}
diff --git a/Step2/kimyeowon/src/test/java/calculator/CalculatorTest.java b/Step2/kimyeowon/src/test/java/calculator/CalculatorTest.java
new file mode 100644
index 0000000..fd12f8c
--- /dev/null
+++ b/Step2/kimyeowon/src/test/java/calculator/CalculatorTest.java
@@ -0,0 +1,35 @@
+package calculator;
+
+import calculator.Calculator;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CalculatorTest {
+
+    private Calculator calculator;
+
+    @BeforeEach
+    public void setUp() {
+        calculator = new Calculator();
+        System.out.println("before");
+    }
+
+    @Test
+    public void add() {
+        assertEquals(30, calculator.add(10, 20));
+    }
+
+    @Test
+    public void substract() {
+        assertEquals(5, calculator.substract(10, 5));
+    }
+
+    @AfterEach
+    public void teardown() {
+        System.out.println("teardown");
+    }
+
+}
diff --git a/Step2/kimyeowon/src/test/java/calculator/StringCalculatorTest.java b/Step2/kimyeowon/src/test/java/calculator/StringCalculatorTest.java
new file mode 100644
index 0000000..1ae7523
--- /dev/null
+++ b/Step2/kimyeowon/src/test/java/calculator/StringCalculatorTest.java
@@ -0,0 +1,54 @@
+package calculator;
+
+import calculator.StringCalculator;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class StringCalculatorTest {
+
+    private StringCalculator stCal;
+
+    @BeforeEach
+    public void setUp() throws Exception {
+        stCal = new StringCalculator();
+    }
+
+    @Test
+    public void add_null_or_emptyText() throws Exception {
+        assertEquals(0, stCal.add(""));
+        assertEquals(0, stCal.add(null));
+    }
+
+    @Test
+    public void add_oneNum() throws Exception {
+        assertEquals(1, stCal.add("1"));
+    }
+
+    @Test
+    public void add_delimiter_comma() throws Exception {
+        assertEquals(3, stCal.add("2, 3"));
+    }
+
+    @Test
+    public void add_delimiter_commaOrColon() throws Exception {
+        assertEquals(3, stCal.add("2:3"));
+        assertEquals(6, stCal.add("1,2:3"));
+    }
+
+    @Test
+    public void add_delimiter_customed() throws Exception {
+        assertEquals(6, stCal.add("//;\n1;2:3"));
+    }
+
+    @Test
+    public void add_negative_num() throws Exception {
+        stCal.add("-2, 2; 3");
+    }
+
+    @AfterEach
+    public void tearDown() throws Exception {
+    }
+
+}