Question

我遇到了通过用户输入更新文本文件的逻辑问题。

我有一个包含产品信息的文本文件（ID;名称;成本;库存）：

001;Hand Soap;2.00;500

为了添加产品，用户调用函数addProduct，以便在产品名称已存在于文件中时更新产品，或者如果文件文件尚不存在则附加到文本文件。我不确定两件事：如何只追加一次（目前它附加的每一行都附加......）以及如何处理空文本文件。

这就是addProduct的外观：

public void addProduct(Product product, int amountReceived) throws FileNotFoundException, IOException {
    newProduct = product;
    String productParams = newProduct.getProduct();
    String productID = newProduct.getProductID();
    int productStock = newProduct.getProductStock();
    String productName = newProduct.getProductName();
    String tempFileName = "tempFile.txt";

    System.out.println("Attempting to Add Product : " + newProduct.getProduct());

    BufferedReader br = null;
    BufferedWriter bw = null;

    try {
        FileInputStream fstream = new FileInputStream(ProductMap.productFile);
        br = new BufferedReader(new InputStreamReader(fstream));
        String line;
        StringBuilder fileContent = new StringBuilder();

        while ((line = br.readLine()) != null) {
            System.out.println("Line : " + line);
            String [] productInfo = line.split(";");
            System.out.println("Added Product Info length : " + productInfo.length);
            if (productInfo.length > 0) {
                if (productInfo[1].equals(productName))
                {
                    System.out.println("Adding existing product");
                    System.out.println("Product Info : " + String.valueOf(productInfo[3]));
                    //line = line.replace(String.valueOf(productInfo), String.valueOf(productStock - amountSold));
                    productInfo[3] = String.valueOf(Integer.parseInt(productInfo[3]) + amountReceived);
                    String newLine = productInfo[0] + ";" + productInfo[1] + ";" + productInfo[2] + ";" + productInfo[3];
                    fileContent.append(newLine);
                    fileContent.append("\n");

                    System.out.println("Updated Product Info : " + String.valueOf(Integer.parseInt(productInfo[3]) + amountReceived));
                    System.out.println("Line :" + newLine);
                } else {
                    fileContent.append(line);
                    fileContent.append("\n");
                    fileContent.append(productParams);
                    fileContent.append("\n");
                    //fileContent.append(productParams + "\n");
                    //System.out.println("Product Name : " + productInfo[1]);
                    //System.out.println("The full product info : " +productParams);
                }

            }
            br.readLine();
        }

        if (br.readLine() == null) {
            fileContent.append(productParams);
        }


        System.out.println("Product Updated File Contents : " + fileContent);
        FileWriter fstreamWrite = new FileWriter(ProductMap.productFile);
        BufferedWriter out = new BufferedWriter(fstreamWrite);
        System.out.println("File Content : " + fileContent);
        out.write(fileContent.toString());
        out.close();

        in.close();
    } catch (Exception e) {
        System.err.println("Error: " + e.getMessage());
    }
}

Answer 1

At a high level, a simple text file may not be the best choice for this use. This implementation requires enough memory to hold the entire file.

If you only had additions and could just append to the file directly, things would be easier. A database would seem to be the best choice. Somewhere between a database and a simple text file, a RandomAccessFile could help if the data could be written with standard lengths for each field. Then you could overwrite a particular row rather than having to rewrite the whole file.

Given the constraints of the current setup, I can't think of a way around writing all the data each time the file is updated.

To get around the empty file problem, you could skip the else condition of the current loop So the new data would not be added to the fileContent StringBuffer. Then when writing the data back out, you could either write the new data before or after the other information from the file.

Also, the readLine at the bottom of the loop is not needed. Any row that is read at the bottom of the loop will be skipped over and not really processed when the read at the top of the loop gets the next line.

更新文本文件的逻辑问题 - Java

1 个答案: