Step2 - 문자열 계산기

src/main/kotlin/Calculation.kt

@@ -0,0 +1,40 @@
+class Calculation {
+
+    fun calcutateByString(input: String?): Int {
+        if(input.isNullOrBlank()) {
+            throw IllegalArgumentException()
+        }
+        val splitedInput = input.split(" ")
+        var result: Int = splitedInput.first().toInt()
+        splitedInput.drop(1).windowed(2, 2).forEach {
+            result = calculate(result, it[1].toInt(), it[0])
+        }
+        return result
+    }
+
+    private fun calculate(first: Int, second: Int, operator: String): Int {
+        return when(operator) {
+            "+" -> add(first, second)
+            "-" -> subtract(first, second)
+            "*" -> multiply(first, second)
+            "/" -> divide(first, second)
+            else -> throw IllegalArgumentException("Using unsupported operators")
+        }
+    }
+
+    private fun add(first: Int, second: Int): Int {
+        return first + second
+    }
+
+    private fun subtract(first: Int, second: Int): Int {
+        return first - second
+    }
+
+    private fun multiply(first: Int, second: Int): Int {
+        return first * second
+    }
+
+    private fun divide(first: Int, second: Int): Int {
+        return first / second
+    }
+}

src/main/kotlin/Person.kt

@@ -0,0 +1,5 @@
+data class Person(
+    val name: String,
+    val age: Int,
+    var nickname: String? = "Guest"
+)

src/test/kotlin/CalcutationTest.kt

@@ -0,0 +1,44 @@
+package study
+
+import Calculation
+import org.assertj.core.api.Assertions
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatThrownBy
+import org.junit.jupiter.api.Test
+
+class CalcutationTest {
+
+    @Test
+    fun `예제 확인`() {
+        assertThat(Calculation().calcutateByString("2 + 3 * 4 / 2"))
+            .isEqualTo(10)
+    }
+
+    @Test
+    fun `입력값이 Null`() {
+        assertThatThrownBy {
+            Calculation().calcutateByString(null)
+        }.isInstanceOf(IllegalArgumentException::class.java)
+    }
+
+    @Test
+    fun `연산자 다를때`() {
+        assertThatThrownBy {
+            Calculation().calcutateByString("2 + 3 * 4 % 2")
+        }.isInstanceOf(IllegalArgumentException::class.java)
+    }
+
+    @Test
+    fun `문자열 처음 슷자가 아닐 때`() {
+        assertThatThrownBy {
+            Calculation().calcutateByString("# + 3 * 4 / 2")
+        }.isInstanceOf(IllegalArgumentException::class.java)
+    }
+
+    @Test
+    fun `문자열 마지막이 숫자가 아닐 때`() {
+        assertThatThrownBy {
+            Calculation().calcutateByString("1 + 3 * 4 / #")
+        }.isInstanceOf(IllegalArgumentException::class.java)
+    }
+}

src/test/kotlin/PersonTest.kt

@@ -1,5 +1,6 @@
 package study
 
+import Person
 import org.assertj.core.api.Assertions.assertThat
 import org.junit.jupiter.api.Test