Question

我试图用我创建的方法读取整个文本文件。文本文件的所有行都按照我的要求打印出来，但打印出来时文件的最后一行显示为null。

private void readFile(String Path) throws IOException{
    String text = ""; //String used in the process of reading a file

    //The file reader
    BufferedReader input = new BufferedReader(
            new FileReader(Path));

    //Creating a new string builder.
    StringBuilder stringBuilder = new StringBuilder();

    while(text != null)
    {
        //Read the next line
        text = input.readLine();

        stringBuilder.append(text); //Adds line of text into the String Builder
        stringBuilder.append(newLine); //Adds a new line using the newLine string
    } 

    //Sets the text that was created with the stringBuilder
    SetText(stringBuilder.toString());
}

所有文件都按原样100％打印出来，除非方法在底部添加一条额外的行，表示“null”我将如何编写代码以便这条线不会出现？

Answer 1

你可以改变这个：

    while(text != null)
    {
        //Read the next line
        text = input.readLine();

        // ... do stuff with text, which might be null now
    }

要么：

    while((text = input.readLine()) != null)
    {
        // ... do stuff with text
    }

或者这个：

    while(true)
    {
        //Read the next line
        text = input.readLine();
        if(text == null)
            break;

        // ... do stuff with text
    }

或者这个：

    text = input.readLine();
    while(text != null)
    {
        // ... do stuff with text

        //Read the next line
        text = input.readLine();
    }

根据您的喜好。

Answer 2

您的循环退出条件位于错误的位置。

while ((text = input.readLine()) != null) {
    stringBuilder.appendText(text)
    ...

Answer 3

使用预读，您将获得一个更清晰的解决方案，这很容易理解：

text = input.readLine();

while(text != null)
    {
        stringBuilder.append(text); //Adds line of text into the String Builder
        stringBuilder.append(newLine); //Adds a new line using the newLine string

        //Read the next line
        text = input.readLine();
    }

使用预读原则，您几乎可以始终避免不良的退出条件。

文件中的最后读取行打印为null

3 个答案: