260630_16_이혁

2026-06-30/src/main/java/com/survivalcoding/Book.java

@@ -0,0 +1,62 @@
+package com.survivalcoding;
+
+import java.util.Date;
+import java.util.Objects;
+
+public class Book implements Cloneable, Comparable<Book> {
+    private String title;
+    private Date publishDate;
+    private String comment;
+
+    public String getTitle() {
+        return title;
+    }
+
+    public void setTitle(String title) {
+        this.title = title;
+    }
+
+    public Date getPublishDate() {
+        return publishDate;
+    }
+
+    public void setPublishDate(Date publishDate) {
+        this.publishDate = publishDate;
+    }
+
+    public String getComment() {
+        return comment;
+    }
+
+    public void setComment(String comment) {
+        this.comment = comment;
+    }
+
+    @Override
+    public final boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof Book book)) return false;
+        return Objects.equals(title, book.title) && Objects.equals(publishDate, book.publishDate);
+    }
+
+    @Override
+    public int hashCode() {
+        int result = Objects.hashCode(title);
+        result = 31 * result + Objects.hashCode(publishDate);
+        return result;
+    }
+
+    @Override
+    public int compareTo(Book other) {
+        return other.publishDate.compareTo(this.publishDate);
+    }
+
+    @Override
+    public Book clone() {
+        Book result = new Book();
+        result.title = this.title;
+        result.publishDate = (Date) this.publishDate.clone();
+        result.comment = this.comment;
+        return result;
+    }
+}

2026-06-30/src/test/java/com/survivalcoding/BookTest.java

@@ -0,0 +1,197 @@
+package com.survivalcoding;
+
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.api.Test;
+
+import java.text.SimpleDateFormat;
+import java.util.*;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class BookTest {
+
+    private Date date(String yyyyMMdd) throws Exception {
+        return new SimpleDateFormat("yyyy-MM-dd").parse(yyyyMMdd);
+    }
+
+    @Test
+    @DisplayName("제목과 출간일이 같으면 equals()는 true를 반환한다")
+    void equals_sameTitleAndDate_returnsTrue() throws Exception {
+        // given
+        Book book1 = new Book();
+        book1.setTitle("자바의 정석");
+        book1.setPublishDate(date("2024-01-01"));
+
+        Book book2 = new Book();
+        book2.setTitle("자바의 정석");
+        book2.setPublishDate(date("2024-01-01"));
+
+        // when
+        boolean result = book1.equals(book2);
+
+        // then
+        assertTrue(result);
+    }
+
+    @Test
+    @DisplayName("제목 또는 출간일이 다르면 equals()는 false를 반환한다")
+    void equals_differentTitleOrDate_returnsFalse() throws Exception {
+        // given
+        Book book1 = new Book();
+        book1.setTitle("자바의 정석");
+        book1.setPublishDate(date("2024-01-01"));
+
+        Book book2 = new Book();
+        book2.setTitle("이펙티브 자바");
+        book2.setPublishDate(date("2024-01-01"));
+
+        // when
+        boolean result = book1.equals(book2);
+
+        // then
+        assertFalse(result);
+    }
+
+    @Test
+    @DisplayName("같다고 판단되는 두 Book은 hashCode도 동일하다")
+    void hashCode_equalBooks_haveSameHashCode() throws Exception {
+        // given
+        Book book1 = new Book();
+        book1.setTitle("자바의 정석");
+        book1.setPublishDate(date("2024-01-01"));
+
+        Book book2 = new Book();
+        book2.setTitle("자바의 정석");
+        book2.setPublishDate(date("2024-01-01"));
+
+        // when
+        int hash1 = book1.hashCode();
+        int hash2 = book2.hashCode();
+
+        // then
+        assertEquals(hash1, hash2);
+    }
+
+    @Test
+    @DisplayName("제목과 출간일이 같은 Book을 Set에 넣으면 동일 객체로 취급되어 하나만 저장된다")
+    void set_sameTitleAndDateBooks_treatedAsSameObject() throws Exception {
+        // given
+        Book book1 = new Book();
+        book1.setTitle("자바의 정석");
+        book1.setPublishDate(date("2024-01-01"));
+
+        Book book2 = new Book();
+        book2.setTitle("자바의 정석");
+        book2.setPublishDate(date("2024-01-01"));
+
+        Set<Book> books = new HashSet<>();
+
+        // when
+        books.add(book1);
+        books.add(book2);
+
+        // then
+        assertEquals(1, books.size());
+    }
+
+    @Test
+    @DisplayName("제목과 출간일이 같은 Book을 Map의 key로 사용하면 동일 키로 취급된다")
+    void map_sameTitleAndDateBooks_treatedAsSameKey() throws Exception {
+        // given
+        Book book1 = new Book();
+        book1.setTitle("자바의 정석");
+        book1.setPublishDate(date("2024-01-01"));
+
+        Book book2 = new Book();
+        book2.setTitle("자바의 정석");
+        book2.setPublishDate(date("2024-01-01"));
+
+        Map<Book, String> map = new HashMap<>();
+
+        // when
+        map.put(book1, "첫 번째 등록");
+        map.put(book2, "두 번째 등록");
+
+        // then
+        assertEquals(1, map.size());
+        assertEquals("두 번째 등록", map.get(book1));
+    }
+
+    @Test
+    @DisplayName("Collections.sort()를 사용하면 출간일이 최신 순(내림차순)으로 정렬된다")
+    void sort_books_orderedByPublishDateDescending() throws Exception {
+        // given
+        Book oldBook = new Book();
+        oldBook.setTitle("오래된 책");
+        oldBook.setPublishDate(date("2020-01-01"));
+
+        Book newBook = new Book();
+        newBook.setTitle("최신 책");
+        newBook.setPublishDate(date("2024-01-01"));
+
+        Book midBook = new Book();
+        midBook.setTitle("중간 책");
+        midBook.setPublishDate(date("2022-01-01"));
+
+        List<Book> books = new ArrayList<>(List.of(oldBook, newBook, midBook));
+
+        // when
+        Collections.sort(books);
+
+        // then
+        assertEquals("최신 책", books.get(0).getTitle());
+        assertEquals("중간 책", books.get(1).getTitle());
+        assertEquals("오래된 책", books.get(2).getTitle());
+    }
+
+    @Test
+    @DisplayName("clone()을 호출하면 필드 값이 동일한 새로운 객체가 생성된다")
+    void clone_returnsBookWithSameFieldValues() throws Exception {
+        // given
+        Book original = new Book();
+        original.setTitle("자바의 정석");
+        original.setPublishDate(date("2024-01-01"));
+        original.setComment("좋은 책");
+
+        // when
+        Book cloned = original.clone();
+
+        // then
+        assertEquals(original.getTitle(), cloned.getTitle());
+        assertEquals(original.getPublishDate(), cloned.getPublishDate());
+        assertEquals(original.getComment(), cloned.getComment());
+    }
+
+    @Test
+    @DisplayName("clone()으로 생성된 객체는 원본과 다른 참조이다")
+    void clone_returnsDifferentReferenceFromOriginal() throws Exception {
+        // given
+        Book original = new Book();
+        original.setTitle("자바의 정석");
+        original.setPublishDate(date("2024-01-01"));
+
+        // when
+        Book cloned = original.clone();
+
+        // then
+        assertNotSame(original, cloned);
+    }
+
+    @Test
+    @DisplayName("clone()은 publishDate를 깊은 복사하므로, 복사본의 날짜를 변경해도 원본은 영향받지 않는다")
+    void clone_publishDate_isDeepCopied() throws Exception {
+        // given
+        Book original = new Book();
+        original.setTitle("자바의 정석");
+        original.setPublishDate(date("2024-01-01"));
+
+        Book cloned = original.clone();
+
+        // when
+        cloned.getPublishDate().setTime(0L); // 복사본의 날짜를 변경
+
+        // then
+        assertNotEquals(original.getPublishDate().getTime(), cloned.getPublishDate().getTime());
+        assertNotSame(original.getPublishDate(), cloned.getPublishDate());
+    }
+}