update:demo3

com/study/demo3/LibraryTest.java

@@ -0,0 +1,44 @@
+package com.study.demo3;
+import java.util.List;
+
+public class LibraryTest {
+    public static void main(String[] args) {
+        Library lib = new Library();
+
+       
+        EBook e1 = new EBook("E001", "Java Basics", 5.2);
+       
+        e1.setAvailable(false); 
+
+       
+        PrintedBook p1 = new PrintedBook("P001", "Design Patterns", 3);
+
+       
+        lib.addBook(e1);
+        lib.addBook(p1);
+
+       
+        lib.addBook(p1);
+
+       
+        System.out.println("\n--- 可借阅图书列表 (available = true) ---");
+        List<Book> availableList = lib.searchAvailableBooks();
+
+        if (availableList.isEmpty()) {
+            System.out.println("No books are currently available for loan.");
+        } else {
+            for (Book book : availableList) {
+               
+                System.out.println("- " + book.getTitle() + " (ISBN: " + book.getIsbn() + ")");
+            }
+        }
+        
+       
+        e1.returnBook(); 
+        System.out.println("\n--- 恢复 e1 后可借阅图书列表 ---");
+        availableList = lib.searchAvailableBooks();
+        for (Book book : availableList) {
+            System.out.println("- " + book.getTitle() + " (ISBN: " + book.getIsbn() + ")");
+        }
+    }
+}