Java - 如何从文本文件中删除空行

Question

我希望能够从文本文件中删除空行，例如：

Average Monthly Disposable Salary
1
Switzerland 
$6,301.73 
2014

2
Luxembourg 
$4,479.80 
2014

3
Zambia 
$4,330.98 
2014

——至此：

Average Monthly Disposable Salary
1
Switzerland 
$6,301.73 
2014
2
Luxembourg 
$4,479.80 
2014
3
Zambia 
$4,330.98 
2014

我拥有的所有代码如下：

public class Driver {

    public static void main(String[] args) 
    throws Exception {

        Scanner file = new Scanner(new File("src/data.txt"));

        PrintWriter write = new PrintWriter("src/data.txt");

        while(file.hasNext()) {
            if (file.next().equals("")) {
                continue;
            } else {
                write.write(file.next());
            }
        }
        print.close();
        file.close();

    }

}

问题是，一旦我回去再次查看该文件，该文本文件就是空的。

我不确定为什么会这样，因为它们似乎都是空白字符，\\n 显示换行符

Answer 1

你的代码几乎是正确的，但有一些错误：

• 您必须使用.nextLine()而不是.next()
• 您必须在读取原始文件时写入另一个文件
• 你的print.close(); 应该是write.close();
• 你忘记在写的每一行后添加一个新行

• 你不需要继续； 指令，因为它是多余的。

   public static void main(String[] args) { Scanner file; PrintWriter writer; try { file = new Scanner(new File("src/data.txt")); writer = new PrintWriter("src/data2.txt"); while (file.hasNext()) { String line = file.nextLine(); if (!line.isEmpty()) { writer.write(line); writer.write("\\n"); } } file.close(); writer.close(); } catch (FileNotFoundException ex) { Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); } }

如果要保留原始名称，可以执行以下操作：

File file1 = new File("src/data.txt");
File file2 = new File("src/data2.txt");

file1.delete();
file2.renameTo(file1);

Answer 2

尝试org.apache.commons.io和 Iterator

try
{
    String name = "src/data.txt";
    List<String> lines = FileUtils.readLines(new File(name));

    Iterator<String> i = lines.iterator();
    while (i.hasNext())
    {
        String line = i.next();
        if (line.trim().isEmpty())
            i.remove();
    }

    FileUtils.writeLines(new File(name), lines);
}
catch (IOException e)
{
    e.printStackTrace();
}

Answer 3

您可以复制到临时文件并重命名。

String name = "src/data.txt";
try(BufferedWriter bw = new BufferedWriter(name+".tmp)) {
    Files.lines(Paths.get(name))
         .filter(v -> !v.trim().isEmpty())
         .forEach(bw::println);
}
new File(name+".tmp").renameTo(new File(name));

Answer 4

这段代码为我解决了这个问题

package linedeleter;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Scanner;

public class LineDeleter {

    public static void main(String[] args) throws FileNotFoundException, IOException {
        File oldFile = new File("src/data.txt"); //Declares file variable for location of file
        Scanner deleter = new Scanner(oldFile); //Delcares scanner to read file
        String nonBlankData = ""; //Empty string to store nonblankdata
        while (deleter.hasNextLine()) { //while there are still lines to be read 
            String currentLine = deleter.nextLine(); //Scanner gets the currentline, stories it as a string
            if (!currentLine.isBlank()) { //If the line isn't blank
                nonBlankData += currentLine + System.lineSeparator(); //adds it to nonblankdata
            }
        }
        PrintWriter writer = new PrintWriter(new FileWriter("src/data.txt"));
        //PrintWriter and FileWriter are declared, 
        //this part of the code is when the updated file is made, 
        //so it should always be at the end when the other parts of the 
        //program have finished reading the file
        writer.print(nonBlankData); //print the nonBlankData to the file
        writer.close(); //Close the writer
    }

}

正如代码块的评论中所提到的，您的示例在您的扫描仪之后声明了打印编写器，这意味着该程序已经覆盖了您当前的同名文件。 因此，您的扫描仪没有代码可以读取，因此程序给了您一个空白文件

这

System.lineSeparator()

只是添加了一个额外的空间，这并不会阻止程序继续在该空间上写入，但是，这一切都很好