Unable to export file!

The program below reads three files (txt1, txt2, txt3) and outputs them to the console, creating and writing three other files (txt4, txt5, txt6).The console outputs the file and creates a file, but all three of the files are "null".Why?

import java.io.*;

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

try{     
BufferedReader reader = new BufferedReader (new FileReader("txt1.txt"));
BufferedReader reader1 = new BufferedReader(new FileReader("txt2.txt"));
BufferedReader reader2 = new BufferedReader(new FileReader("txt3.txt"));

String line;

while(null!=(line=reader.readLine())){
    System.out.println(line);
}

String line 1;
while(null!=(line1=read1.readLine())){
    System.out.println(line1);
}

String line 2;

while(null!=(line2=reader2.readLine())){
    System.out.println(line2);
}

reader.close();
reader1.close();
reader2.close();

File file=new File("txt4.txt");
File file1 = new File("txt5.txt");
File file2 = new File("txt6.txt");
file.createNewFile();
file1.createNewFile();
file2.createNewFile();
PrintWriter writer = new PrintWriter(new BufferedWriter(newFileWriter(file)));
PrintWriter writer1 = new PrintWriter(new BufferedWriter(newFileWriter(file1))));
PrintWriter writer2 = new PrintWriter(new BufferedWriter(newFileWriter(file2));

writer.println(line);
writer1.println(line1);
writer2.println(line2);

writer.close();
writer1.close();
writer2.close();
}

catch(IOExceptione){}

}
}

java

2022-10-28 10:16

1 Answers

For example, if you look at the variable line,

String line;

while(null!=(line=reader.readLine())){
    System.out.println(line);
}

Continue to perform the actions in the while loop above unless line is null
Conversely, line is always null when you exit the while loop.

Therefore, subsequent actions

writer.println(line);

The value of line when running is also naturally null.

while(null!=(line=read.readLine())){
    System.out.println(line);
}

Now that you want to export the values that are outputting to the console to a file, you can also output the file here.

import java.io.*;

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

        try{
            BufferedReader reader = new BufferedReader (new FileReader("txt1.txt"));
            BufferedReader reader1 = new BufferedReader(new FileReader("txt2.txt"));
            BufferedReader reader2 = new BufferedReader(new FileReader("txt3.txt"));
            
            File file=new File("txt4.txt");
            File file1 = new File("txt5.txt");
            File file2 = new File("txt6.txt");
            file.createNewFile();
            file1.createNewFile();
            file2.createNewFile();
            PrintWriter writer = new PrintWriter(new BufferedWriter(newFileWriter(file)));
            PrintWriter writer1 = new PrintWriter(new BufferedWriter(newFileWriter(file1))));
            PrintWriter writer2 = new PrintWriter(new BufferedWriter(newFileWriter(file2));


            String line;

            while(null!=(line=reader.readLine())){
                System.out.println(line);
                writer.println(line);
            }

            String line 1;
            while(null!=(line1=read1.readLine())){
                System.out.println(line1);
                writer1.println(line1);
            }

            String line 2;

            while(null!=(line2=reader2.readLine())){
                System.out.println(line2);
                writer2.println(line2);
            }

            reader.close();
            reader1.close();
            reader2.close();



            writer.close();
            writer1.close();
            writer2.close();
        }

        catch(IOExceptione){
        }

    }
}

2022-10-28 10:16

If you have any answers or tips

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