From 4c5eb89e592340cd907b8389a61409ae8edbf95c Mon Sep 17 00:00:00 2001
From: Jason Lu <wjlukuan@hotmail.com>
Date: Thu, 10 Apr 2025 10:53:05 +0800
Subject: [PATCH] Add demo for using enum to create singleton

---
 src/main/java/feature/Book.java     | 35 +++++++++++++++++++++++++++++
 src/main/java/feature/BookDemo.java | 15 +++++++++++++
 src/main/java/feature/BookEnum.java | 14 ++++++++++++
 3 files changed, 64 insertions(+)
 create mode 100644 src/main/java/feature/Book.java
 create mode 100644 src/main/java/feature/BookDemo.java
 create mode 100644 src/main/java/feature/BookEnum.java

diff --git a/src/main/java/feature/Book.java b/src/main/java/feature/Book.java
new file mode 100644
index 0000000..8d38f48
--- /dev/null
+++ b/src/main/java/feature/Book.java
@@ -0,0 +1,35 @@
+package feature;
+
+public class Book {
+    private String title;
+    private String author;
+    private int pages;
+
+    public Book(String title, String author, int pages) {
+        this.title = title;
+        this.author = author;
+        this.pages = pages;
+    }
+
+    public String getTitle() {
+        return title;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public int getPages() {
+        return pages;
+    }
+
+    @Override
+    public String toString() {
+        return "Book{" +
+                "title='" + title + '\'' +
+                ", author='" + author + '\'' +
+                ", pages=" + pages +
+                '}';
+    }
+    
+}
diff --git a/src/main/java/feature/BookDemo.java b/src/main/java/feature/BookDemo.java
new file mode 100644
index 0000000..4b6065d
--- /dev/null
+++ b/src/main/java/feature/BookDemo.java
@@ -0,0 +1,15 @@
+package feature;
+
+/**
+ * create singleton using enum
+ */
+public class BookDemo {
+    public static void main(String[] args) {
+        Book book = new Book("Java Programming", "John Doe", 300);
+        System.out.println(book);
+
+        // Using the singleton pattern
+        BookEnum.INSTANCE.setBook(book);
+        System.out.println(BookEnum.INSTANCE.getBook());
+    }
+}
diff --git a/src/main/java/feature/BookEnum.java b/src/main/java/feature/BookEnum.java
new file mode 100644
index 0000000..ba1ed7e
--- /dev/null
+++ b/src/main/java/feature/BookEnum.java
@@ -0,0 +1,14 @@
+package feature;
+
+public enum BookEnum {
+    INSTANCE;
+
+    private Book book;
+    
+    public Book getBook() {
+        return book;
+    }
+    public void setBook(Book book) {
+        this.book = book;
+    }
+}