Question

在输出文件“CMFTSwitchesnew.txt”中只有输入文件的最后一行。我已经测试了一些不同的方法，比如改变write.println（input.nextLine（）），但我现在还不确定问题出在哪里。

package WorkingWithFiles;


import java.io.*;
import java.util.Scanner;

public class FileIO
{
    public static void main(String[] args)
    {

        File output = new File("CMFTSwitchesNew.txt");
        File source = new File("src/CMFTSwitches.txt");

        try {
            Scanner input = new Scanner(source);

            while (input.hasNextLine()) {

                try {

                    PrintWriter write = new PrintWriter(output);
                    String text = input.nextLine();
                    write.println(text) // also tried 
                                        // write.println(input.nextLine());
                    write.close();

                } catch (Exception e) {

                    System.out.println("Exception found");
                }

            }
        } catch (FileNotFoundException e) {

            System.out.println("The file was not found");
        }
    }
}

Answer 1

           try {

                PrintWriter write = new PrintWriter(output);
                String text = input.nextLine();
                write.println(text) // also tried 
                                    // write.println(input.nextLine());
                write.close();

            } catch (Exception e) {

                System.out.println("Exception found");
            }

您在每次迭代中创建PrintWriter而不使用允许您告知PrintWriter在现有文件末尾附加数据的构造函数。这样您只能看到上次写入文件的输出。要么改为

PrintWriter write = new PrintWriter(output, true);

或在PrintWriter循环之外实例化while并在其后关闭它。

输出文件仅显示输入文件的最后一行

1 个答案: