文件中最后读取的行打印为null

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会按照我的意愿打印出来，但文件打印出来时的最后一行在打印出来时显示为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());
}

除了该方法在底部添加了一行额外的"null"外，所有文件都会100%打印出来。我该如何编写代码，使这一行根本不会出现？

Answer 1

您可以更改：

    while(text != null)
    {
        //Read the next line
        text = input.readLine();
        // ... do stuff with text, which might be null now
    }

要么是：

    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，您将获得更清洁的解决方案，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();
    } 

使用预读原理，您几乎总是可以避免糟糕的退出条件。