实战案例：理解Java集合框架并实现数据增删改查

原创末蓝、 2024-10-16 00:18 40阅读 0赞

在Java编程中，集合框架是一个强大的工具，用于管理和操作多个元素。这里我们将通过一个简单的实战案例来理解和使用Java的集合框架。

案例需求：
设计一个图书管理系统，包括添加书籍、删除书籍、更新书籍信息和查询所有书籍的功能。

1. 创建类（如Book）并实现equals()和hashCode()方法以支持集合中元素的比较。

```java
public class Book {
    private String title;
    private String author;
    private Date publicationDate;

// getters and setters

@Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        Book book = (Book) obj;
        return title.equals(book.getTitle())
                && author.equals(book.getAuthor())
                && publicationDate.equals(book.publicationDate);
    }

@Override
    public int hashCode() {
        int result = title.hashCode();
        result += 31 * (result + author.hashCode()));
        result += 31 * (result + publicationDate.hashCode()));
        return result;
    }
}
```

2. 创建集合类（如BookCollection）并实现add(), remove(), update(), and getAll()方法。

```java
import java.util.ArrayList;
import java.util.List;

public class BookCollection {
    private List<Book> books = new ArrayList<>();

// add, remove, update methods
    public void addBook(Book book) {
        books.add(book);
    }

public void removeBook(Book book) {
        if (books.contains(book)) {
            books.remove(book);
        } else {
            System.out.println("Book not found in collection.");
        }
    }

public void updateBook(Book oldBook, Book newBook) {
        if (books.contains(oldBook))) {
            books.remove(oldBook);
            addBook(newBook);
        } else {
            System.out.println("Old book not found in collection.");
        }
    }

// get all method
    public List<Book> getAllBooks() {
        return books;
    }
}
```

3. 在主类中创建BookCollection实例，进行数据增删改查。

```java
public class Main {
    public static void main(String[] args) {
        Book book1 = new Book("The Catcher in the Rye", "J.D. Salinger", new Date(1951, 7, 16)));
        Book book2 = new Book("To Kill a Mockingbird", "Harper Lee", new Date(1960, 8, 14)));

BookCollection bookCollection = new BookCollection();
        bookCollection.addBook(book1);
        bookCollection.addBook(book2);

// 数据增删改查
        System.out.println("Before update:");
        bookCollection.getAllBooks().forEach(book -> {
            System.out.println("Title: " + book.getTitle() + ", Author: " + book.getAuthor());
        }));
        
        // 更新数据
        book1.setTitle("The Great Gatsby");
        bookCollection.updateBook(book1, book2));

System.out.println("\nAfter update:");
        bookCollection.getAllBooks().forEach(book -> {
            System.out.println("Title: " + book.getTitle() + ", Author: " + book.getAuthor());
        }));
    }
}
```

这个实战案例展示了如何使用Java的集合框架来管理图书数据。包括创建Book类，实现equals和hashCode方法，以及创建BookCollection类进行数据增删改查。