从 Java 中的文件生成的数组中删除文本

Question

我对 Java 比较了解，并且对于个人项目，我正在尝试编写一个程序，该程序可以接受用户输入以写入文本文件并从一行中删除文本（由数组的索引）来自从同一文本文件构建的数组，这样当您打印出文件的内容时，您删除的内容确实被删除了。

这是我的代码，对于我看不到的任何其他错误，我深表歉意：

public class Writing {
    Scanner input = new Scanner(System.in);
    File customerFile = new File("Customers.txt");
    String[] fileArray;

public Writing() throws IOException{
    FileReader fileReader = new FileReader(customerFile);
    BufferedReader bufferedReader = new BufferedReader(fileReader);
    List<String> lines = new ArrayList<String>();
    String line = null;

    while ((line = bufferedReader.readLine()) != null) {
        lines.add(line);
    }
    bufferedReader.close();
    fileArray = lines.toArray(new String[lines.size()]);
}
public void FileWrite() throws IOException {

        String inputData = input.nextLine();
        if (!customerFile.exists()) {
            customerFile.createNewFile();

        }
        FileWriter fileWriter = new FileWriter(customerFile.getName(),true);
        BufferedWriter bufferWriter = new BufferedWriter(fileWriter);
        bufferWriter.write(inputData + "\n");
        bufferWriter.close();

        System.out.println("Done.");
}

//Here is the one I have trouble with
public void RemoveFile() throws IOException {
    LinkedList<String> cusList = new LinkedList<String>(Arrays.asList(fileArray));

    System.out.println("Which one would you like to delete? [0-#].");
    //then it prints the list so you can see what you want to delete

        for(String x: cusList){
            System.out.println(x);
        }

            String removeThis = input.nextLine();
            int removeNum = Integer.parseInt(removeThis);
            if()){ //if the user input contains the number that occurs as an index in the list
                //not sure what to put here
                    fileArray = cusList.toArray(fileArray);

            }else{
                System.out.println("Remove failed.");
            }
}
}

我被困住了，因为尽管过去曾尝试解决这个问题，但我最终还是收到了我的 else 语句，或者文本文件没有任何变化。

编辑：以下是我为解决此问题所做的主要尝试，但无济于事。 这是在 RemoveFile() 中 class。

失败的方法：

    //tries to remove the element if it is found, before I decided to jusr remove the index
    //example: if "Cocoa Powder" is typed in and it exists within the list of the array created from the file, remove it.

if(cusList.contains(removeThis)){
cusList.remove(removeThis);
cusList.toArray(fileArray);
}
//the else statement here saying that it failed

方法二失败：

   //attempts to remove the content of the inputted index within the list 

if(removeNum.equals(cusList.indexOf(removeNum))){
    cusList.remove(removeNum);
    cusList.toArray(fileArray);
}

//else statement would go here

求助！

解决方法：我想通了，感谢所有提供帮助的人，我意识到一个更简单的解决方案是清除文本文件的所有内容，使用包含所有内容的数组，然后将这些内容写回所有更改后的文本文件。这是我的代码：

   // RemoveFile method
    public void RemoveFile() throws IOException {
        LinkedList<String> cusList = new LinkedList<String>(
            Arrays.asList(fileArray));

    System.out.println("Which one would you like to delete? Each customer is given a number [1-#].");
    System.out.println("The file will change when program terminated.");
    for (int i = 1; i < fileArray.length; i++) {
        for (String x : cusList) {
            System.out.println("Customer " + i + ": " + x);
            i++;
        }
    }

    String removeThis = input.nextLine();
    int removedNum = Integer.parseInt(removeThis);
    int removeNum = removedNum - 1;
    if (removeNum >= 0 && removeNum < cusList.size()) {
        cusList.remove(removeNum);
        fileArray = cusList.toArray(fileArray);

        PrintWriter writer = new PrintWriter(customerFile);
        writer.print("");// clears the file contents
        writer.close();

        FileWriter fileWriter = new FileWriter(customerFile.getName(), true);
        BufferedWriter bufferWriter = new BufferedWriter(fileWriter);

        for (String x : cusList) {
            bufferWriter.write(x + "\n");

        }
        bufferWriter.close();
    } else {
        System.out.println("Index out of bounds, " + removeNum + " >= "
                + cusList.size());
    }

这似乎工作得很好而且 MadProgrammer 的建议使逻辑工作，而不是不断地返回 false 然后允许程序从文件中提取数据到一个数组中，清除数组的内容，然后写入它回到文件中。

Answer 1

custList 包含来自文件的 String 值列表，contains 将始终 return false，因为它正在寻找匹配中的相等性（例如 1 != "some string value"）。

你需要做一些更像 if (removeNum >= 0 && removeNum < cusList.size()) 的事情，然后你知道该值在 List 的范围内，然后你可以简单地使用 removeNum 删除值给定的索引，custList.remove(removeNum)

if (removeNum >= 0 && removeNum < cusList.size()) { 
    custList.remove(removeNum);
}else{
    System.out.println("Index out of bounds, " + removeNum + " >= " + custList.size());
}

Answer 2

File inFile = new File("input.dat");
File outFile = new File("output.dat");
Scanner scan = new Scanner(inFile);
PrintWriter out = new PrintWriter(outFile);
while(scan.hasNextLine()) {
    String line = scan.nextLine();
    if(<criterion_to_determine_whether_to_keep_line_or_not>) {
        out.println(line);
    }
}
scan.close();
out.close();

原则上，您不应尝试编辑作为输入收到的文件，而应使用更改后的输出编写一个新文件。如果您确实需要新文件与旧文件同名，请对两个文件执行 File.renameTo()。

从 Java 中的文件生成的数组中删除文本

Removing Text from an Array Made From a File in Java

java

arrays

list

text-files

file-writing