#18 oop : grade calculator

oop/oop-practice/oop-practice/src/main/java/org/example/grade/Course.java

@@ -0,0 +1,49 @@
+package org.example.grade;
+
+public class Course {
+
+    private final String subject; // 과목명
+    private final int credit; // 학점
+    private final String grade; // 성적
+
+    public Course(String subject, int credit, String grade) {
+        this.subject = subject;
+        this.credit = credit;
+        this.grade = grade;
+    }
+
+    public double multiplyCreditAndCourseGrade() {
+        return credit * getGradeToNumber();
+    }
+
+    public int getCredit() {
+        return credit;
+    }
+
+    public double getGradeToNumber() {
+        double grade = 0;
+
+        switch (this.grade) {
+            case "A+":
+                grade = 4.5;
+                break;
+            case "A":
+                grade = 4.0;
+                break;
+            case "B+":
+                grade = 3.5;
+                break;
+            case "B":
+                grade = 3.0;
+                break;
+            case "C+":
+                grade = 2.5;
+                break;
+            case "C":
+                grade = 2.0;
+                break;
+        }
+        return grade;
+    }
+
+}

oop/oop-practice/oop-practice/src/main/java/org/example/grade/Courses.java

@@ -0,0 +1,24 @@
+package org.example.grade;
+
+import java.util.List;
+
+public class Courses {
+
+    private final List<Course> courses;
+
+    public Courses(List<Course> courses) {
+        this.courses = courses;
+    }
+
+    public double multiplyCreditAndCourseGrade() {
+        return courses.stream()
+                .mapToDouble(Course::multiplyCreditAndCourseGrade)
+                .sum();
+    }
+
+    public int calculateTotalCompletedCredit() {
+        return courses.stream()
+                .mapToInt(Course::getCredit)
+                .sum();
+    }
+}

oop/oop-practice/oop-practice/src/main/java/org/example/grade/GradeCalculator.java

@@ -0,0 +1,18 @@
+package org.example.grade;
+
+import java.util.List;
+
+public class GradeCalculator {
+    private final Courses courses;
+    public GradeCalculator(List<Course> courses) {
+        this.courses = new Courses(courses);
+    }
+
+    public double calculateGrade() {
+
+        double multiplyCreditAndCourseGrade = courses.multiplyCreditAndCourseGrade();
+        int totalCompletedCredit = courses.calculateTotalCompletedCredit();
+
+        return multiplyCreditAndCourseGrade / totalCompletedCredit;
+    }
+}

oop/oop-practice/oop-practice/src/test/java/org/example/grade/CourseTest.java

@@ -0,0 +1,16 @@
+package org.example.grade;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThatCode;
+
+public class CourseTest {
+
+    @DisplayName("과목(코스)를 생성한다.")
+    @Test
+    void createTest() {
+        assertThatCode(() -> new Course("OOP", 3, "A+"))
+                .doesNotThrowAnyException();
+    }
+}

oop/oop-practice/oop-practice/src/test/java/org/example/grade/GradeCalculatorTest.java

@@ -0,0 +1,30 @@
+package org.example.grade;
+
+import org.assertj.core.api.Assertions;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.util.List;
+
+import static org.assertj.core.api.Assertions.*;
+
+/**
+ * 평균학점 계산 방법 = (학점 * 성적)의 합계 / 수강신청 총학점 수
+ * 일급 컬렉션 사용
+ */
+public class GradeCalculatorTest {
+
+    @DisplayName("평균 학점을 계산한다.")
+    @Test
+    void calculateGradeTest() {
+        List<Course> courses = List.of(
+                new Course("OOP", 3, "A+"),
+                new Course("자료구조", 3, "A+")
+        );
+
+        GradeCalculator gradeCalculator = new GradeCalculator(courses);
+        double gradeResult = gradeCalculator.calculateGrade();
+
+        assertThat(gradeResult).isEqualTo(4.5);
+    }
+}