java - ArrayList 从文件中读取行并分配它们

Question

我创建了一个从文件中读取的代码，每一行都是一本不同的书，每一行都包含一个标题和价格。书籍文件是:

    The Hobbit,$15.00
    Purple Cow,$10.00
    Death by Black Hole,$35.00

这些方法有效。但我正在尝试创建一种方法，其工作原理如下:输入预算:15，然后显示 15 美元以下的所有书籍。我已经完成了 searchForPrice 方法的一部分，但它并没有真正发挥作用。我怎样才能做到呢？谢谢。

import java.util.*;
import java.io.*;
import javax.swing.*;
public class BookStore {
    private ArrayList<Book> library;
    String Book;

    public BookStore() throws FileNotFoundException {
        library = readBooks("books1.txt");
    }
    public ArrayList<Book> readBooks(String path) {
        ArrayList<Book> books = new ArrayList<Book>();

        try{
            BufferedReader br = new BufferedReader(new FileReader(path));
            String line;
            while ((line = br.readLine()) != null) {
                String[] arr = line.split(",");
                String title = arr[0];
                double price = Double.parseDouble(arr[1].trim().replace("$",""));//in case has a $
                books.add(new Book(title,price));

            }
            br.close();
        }
        catch (Exception e){
            e.printStackTrace();
        }
        return books;
    }

    public String toString() {
        String result = "";
        for (Book tempBook : library) {
            result += tempBook.toString() + "\n";
        }
        return result;
    }

    public ArrayList<Book> searchForTitle(String searchString) {
        ArrayList<Book> searchResult = new ArrayList<Book>();
        for (Book currentBook : library) {
            if ((currentBook.getTitle()).indexOf(searchString) != -1)
                searchResult.add(currentBook);
        }
        searchResult.trimToSize();
        return searchResult;
    }

    //get lowest price book
    public Book lowestPrice() {
        Book lowestPrice = library.get(0);
        for (Book book : library) {
            if (book.getPrice() < lowestPrice.getPrice()) {
                lowestPrice = book;
            }
        }
        return lowestPrice;
    }

    //bookslessthanthenumbertheyenter
    public ArrayList<Book> searchForPrice(double searchdouble) {
        ArrayList<Book> searchPrice = new ArrayList<Book>();
        for (Book currentBook : library) {
            if ((currentBook.getPrice()).Double.parseDouble.indexOf(searchdouble) != -1)
                searchPrice.add(currentBook);
        }
        searchPrice.trimToSize();
        return searchPrice;
    }
}

Answer 1

这个循环是否编译:

for (Book currentBook : library) {
    if ((currentBook.getPrice()).Double.parseDouble.indexOf(searchdouble) != -1)
        searchPrice.add(currentBook);
}

在Book类中，您将价格存储为double，因此不需要转换，只需将每本书的价格与searchdouble进行比较即可:

for (Book currentBook : library) {
    if (currentBook.getPrice() < searchdouble)
        searchPrice.add(currentBook);
}

还有为什么你需要:

searchPrice.trimToSize();

因为您没有声明任何初始容量？