问题

// 创建名为htmltext的File类型
File htmltext = new File(filepath);
Scanner file = new Scanner(htmltext);

PrintWriter out = new PrintWriter("updated.txt");

while (file.hasNext()) {
    String s = file.nextLine();
    out.println(s);
}
out.close();

运行代码后，out.println(s) 只打印了文本文件的第一行。我查阅了如何将字符串打印到文本文件中，发现应该使用 PrintWriter。我期望程序基本上会使用 PrintWriter 将文本文档的内容“重新打印”到 "updated.txt" 文件中。
然而，似乎它只是将文本文件的第一行“重新打印”到 "updated.txt" 中。

我认为 while 循环有问题，因此我尝试使用 System.out.println(s) 定期将其打印到控制台，但那样却正常工作。

我对 while 循环的理解是，在文件有标记的情况下，它将进行迭代，s 将存储一行，并且（应该）打印该字符串 s。

我错过了什么？我是否误解了 while 循环的工作原理？或者是如何使用 nextLine()？又或者是 PrintWriter 的工作原理。（可能是以上所有原因...）

我希望能得到反馈！

<details>
<summary>英文:</summary>

I want the program to save each line of the text file i have into String s and print String s with a PrintWriter into another text file. 

```//creates creates type File with name htmltext
		File htmltext = new File(filepath);
		Scanner file = new Scanner(htmltext);
		
		PrintWriter out = new PrintWriter(&quot;updated.txt&quot;);
				
		while (file.hasNext()) {
			String s = file.nextLine();	
			out.println(s);
			out.close();

I've run the code and out.println(s), only printed out the first time of the text file.
I looked up how to print string into a text file and I found that I should use PrintWriter.
I was expecting the program to basically "re-print" the content of the text document into the "updated.txt" file using PrintWriter.
However, it only seems to be "re-printing" out the first line of the text file into "updated.txt".

I thought something was wrong with my while loop so I tried printing it out regularly into the console using System.out.println(s), but that worked fine.

What I understand of the while-loop is that while the file has tokens, it will iterate and s will store one line and (it should) print said string s.

What am I missing? Am I misunderstanding how the while-loop works? or how nextLine() works? or how PrintWriter works.(probably all of the above...)

I would love feedbacks!

答案1

得分: 0

你正在告诉它在写入该行后立即关闭。

你想要将 out.close 移动到 while 循环的外部，你也应该可能需要刷新流。

你的代码，用英语表达，基本上是这样的：

从标准输入打开一个扫描器
为文件打开一个打印写入器

当扫描器有新行时
    将新行写入打印写入器
    **关闭打印写入器**

打印写入器关闭后，就无法再写入新数据，因为它已经关闭。

while the scanner has a new line
    write the new line to the printwriter
    **close the printwriter**

答案2

得分: 0

不要在循环内关闭PrintWriter。在while循环之后关闭。

答案3

得分: 0

不要在完成读取整个内容之前关闭write对象

File htmltext = new File(filepath);
Scanner file = new Scanner(htmltext);
PrintWriter out = new PrintWriter("updated.txt");
while (file.hasNext()) 
{
    String s = file.nextLine(); 
    out.println(s);
}

**out.close();**

File htmltext = new File(filepath);
Scanner file = new Scanner(htmltext);
PrintWriter out = new PrintWriter("updated.txt");
while (file.hasNext()) 
{
String s = file.nextLine(); 
out.println(s);
}

**out.close();**