style:fmt

com/study/demo3/Bicycle.java

@@ -0,0 +1,8 @@
+package com.study.demo3;
+
+public class Bicycle extends Vehicle {
+  @Override
+  public void start() {
+    System.out.println("The bike is started");
+  }
+}

com/study/demo3/Book.java

@@ -0,0 +1,57 @@
+package com.study.demo3;
+
+public class Book {
+  protected String isbn;
+  protected String title;
+  protected boolean available;
+
+  public Book() {
+    this.available = true;
+  }
+
+  public Book(String isbn, String title) {
+    this.isbn = isbn;
+    this.title = title;
+    this.available = true;
+  }
+
+  public Book(String isbn, String title, boolean available) {
+    this.isbn = isbn;
+    this.title = title;
+    this.available = available;
+  }
+
+  public String getIsbn() {
+    return isbn;
+  }
+
+  public void setIsbn(String isbn) {
+    this.isbn = isbn;
+  }
+
+  public String getTitle() {
+    return title;
+  }
+
+  public void setTitle(String title) {
+    this.title = title;
+  }
+
+  public boolean isAvailable() {
+    return available;
+  }
+
+  public void setAvailable(boolean available) {
+    this.available = available;
+  }
+
+  public void returnBook() {
+    if (!this.available) {
+      this.available = true;
+      System.out.println(
+          this.title + " (ISBN: " + this.isbn + ") has been returned and is now available.");
+    } else {
+      System.out.println(this.title + " (ISBN: " + this.isbn + ") is already available.");
+    }
+  }
+}

com/study/demo3/Car.java

@@ -0,0 +1,8 @@
+package com.study.demo3;
+
+public class Car extends Vehicle {
+  @Override
+  public void start() {
+    System.out.println("The car is started");
+  }
+}

com/study/demo3/EBook.java

@@ -0,0 +1,35 @@
+package com.study.demo3;
+
+public class EBook extends Book {
+  private double fileSize;
+
+  public EBook() {
+    super();
+  }
+
+  public EBook(String isbn, String title, double fileSize) {
+    super(isbn, title);
+    this.fileSize = fileSize;
+  }
+
+  public double getFileSize() {
+    return fileSize;
+  }
+
+  public void setFileSize(double fileSize) {
+    this.fileSize = fileSize;
+  }
+
+  @Override
+  public String toString() {
+    return "EBook [ISBN="
+        + isbn
+        + ", Title="
+        + title
+        + ", FileSize="
+        + fileSize
+        + "MB, Available="
+        + available
+        + "]";
+  }
+}

com/study/demo3/Library.java

@@ -0,0 +1,37 @@
+package com.study.demo3;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class Library {
+
+  private Map<String, Book> books;
+
+  public Library() {
+    this.books = new HashMap<>();
+  }
+
+  public void addBook(Book b) {
+    String isbn = b.getIsbn();
+
+    if (books.containsKey(isbn)) {
+      System.out.println("The book already exists, adding it failed.");
+    } else {
+      books.put(isbn, b);
+      System.out.println("Book added successfully: " + b.getTitle());
+    }
+  }
+
+  public List<Book> searchAvailableBooks() {
+    List<Book> availableBooks = new ArrayList<>();
+
+    for (Book book : books.values()) {
+      if (book.isAvailable()) {
+        availableBooks.add(book);
+      }
+    }
+    return availableBooks;
+  }
+}

com/study/demo3/LibraryTest.java

@@ -0,0 +1,39 @@
+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() + ")");
+    }
+  }
+}

com/study/demo3/Main3.java

@@ -0,0 +1,30 @@
+package com.study.demo3;
+
+public class Main {
+  public static void main(String[] args) {
+
+    System.out.println("--- 测试 EBook ---");
+
+    EBook ebook = new EBook("123-456", "Java Programming", 2.5);
+    System.out.println("EBook Status (Initial): " + ebook.toString());
+
+    ebook.setAvailable(false);
+    System.out.println("EBook Status (Borrowed): " + ebook.toString());
+
+    ebook.returnBook();
+    System.out.println("EBook Status (After Return): " + ebook.toString());
+
+    System.out.println("\n--- 测试 PrintedBook ---");
+    PrintedBook pbook = new PrintedBook();
+    pbook.setIsbn("789-012");
+    pbook.setTitle("Python Guide");
+    pbook.setStock(10);
+    System.out.println("PBook Status (Initial): " + pbook.toString());
+
+    pbook.setAvailable(false);
+    System.out.println("PBook Status (Borrowed): " + pbook.toString());
+
+    pbook.returnBook();
+    System.out.println("PBook Status (After Return): " + pbook.toString());
+  }
+}

com/study/demo3/PrintedBook.java

@@ -0,0 +1,35 @@
+package com.study.demo3;
+
+public class PrintedBook extends Book {
+  private int stock;
+
+  public PrintedBook() {
+    super();
+  }
+
+  public PrintedBook(String isbn, String title, int stock) {
+    super(isbn, title);
+    this.stock = stock;
+  }
+
+  public int getStock() {
+    return stock;
+  }
+
+  public void setStock(int stock) {
+    this.stock = stock;
+  }
+
+  @Override
+  public String toString() {
+    return "PrintedBook [ISBN="
+        + isbn
+        + ", Title="
+        + title
+        + ", Stock="
+        + stock
+        + ", Available="
+        + available
+        + "]";
+  }
+}

com/study/demo3/StudentManager.java

@@ -0,0 +1,29 @@
+package com.study.demo3;
+
+import java.util.*;
+
+public class StudentManager {
+  public static void main(String[] args) {
+    List<String> studentNames = new ArrayList<>();
+    Map<String, Integer> studentScores = new HashMap<>();
+
+    studentNames.add("张三");
+    studentNames.add("李四");
+    studentNames.add("王五");
+
+    studentScores.put("张三", 85);
+    studentScores.put("李四", 77);
+    studentScores.put("王五", 99);
+
+    System.out.println("--- 所有学生姓名 ---");
+    for (String name : studentNames) {
+      System.out.println(name);
+    }
+
+    studentScores.put("张三", 70);
+
+    Integer zhangsanScore = studentScores.get("张三");
+    System.out.println("\n--- 修改后张三的成绩 ---");
+    System.out.println("张三的成绩: " + zhangsanScore);
+  }
+}

com/study/demo3/Train.java

@@ -0,0 +1,8 @@
+package com.study.demo3;
+
+public class Train extends Vehicle {
+  @Override
+  public void start() {
+    System.out.println("The train is started");
+  }
+}

com/study/demo3/Vehicle.java

@@ -0,0 +1,21 @@
+package com.study.demo3;
+
+public class Vehicle {
+  protected String name;
+
+  public Vehicle(String name) {
+    this.name = name;
+  }
+
+  public Vehicle() {
+    this.name = "Unknown Vehicle";
+  }
+
+  public void start() {
+    System.out.println("Vehicle Start");
+  }
+
+  public void stop() {
+    System.out.println("Vehicle Stop");
+  }
+}