Java read from one file and write into another file using methods

Question

I am learning Java and working on File IO and right now stuck in reading text from One file and write in another file. I am using two different methods first one for reading and displaying text in console from file #1 and using another method to write in file#2.

I can successfully read and display contents from File#1 but not sure how to write the text in file#2.

Here is the code which I have written so far:

import java.io.*;
public class ReadnWrite {
    public static void readFile() throws IOException {
        BufferedReader inputStream = new BufferedReader(new FileReader(
                "original.txt"));
        String count;
        while ((count = inputStream.readLine()) != null) {
            System.out.println(count);
        }
        inputStream.close();
    }
    public static void writeFile() throws IOException{
        BufferedWriter outputStream = new BufferedWriter(new FileWriter(
        "numbers.txt"));

//Not sure what comes here
    }
    public static void main(String[] args) throws IOException {
        checkFileExists();
        readFile();
    }
}

This is just for my own learning as there are lots of examples to read and write without using different methods but I want tolearn how I can achieve through different methods.

Any help will be highly appreciated.

Regards,

You want to read from original.txt and write everything to numbers.txt? — jnd
– jnd, Commented Feb 3, 2015 at 3:55
O comon man, use your common sense. The link is using the code written inside Main method. I can easily achieve that thing but I want to use two different methods without using Reader object in write method. — Newbie
– Newbie, Commented Feb 3, 2015 at 4:11
#Farhang Amary, kindly read through the question properly before posting any possible duplicate question. I have gone through the link and that is using writing to a file in Main() and also I do not want to write any stupid "HELLO WORLD" text by myself. I want to write whatever I am reading from file#1 (original.txt) and write it into file#2(numbers.txt). — Newbie
– Newbie, Commented Feb 3, 2015 at 4:24

jnd · Accepted Answer · 2015-02-03 04:18:20Z

5

You can write to another file using: outputStream.write(). And when you are done just outputStream.flush() and outputStream.close().

Edit:

public void readAndWriteFromfile() throws IOException {
    BufferedReader inputStream = new BufferedReader(new FileReader(
            "original.txt"));
     File UIFile = new File("numbers.txt");
        // if File doesnt exists, then create it
        if (!UIFile.exists()) {
            UIFile.createNewFile();
        }
    FileWriter filewriter = new FileWriter(UIFile.getAbsoluteFile());
    BufferedWriter outputStream= new BufferedWriter(filewriter);
    String count;
    while ((count = inputStream.readLine()) != null) {
        outputStream.write(count);
    }
    outputStream.flush();
    outputStream.close();
    inputStream.close();

edited Feb 3, 2015 at 4:18

answered Feb 3, 2015 at 3:57

jnd

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6 Comments

Newbie Over a year ago

Thanks #jnd but if I try by just giving outputStream.write(); java gives me error that Missing argument to match .write( ) and also how does java know that what I want to save in the file. I believe I have to put all the text from original.txt file in to an object or an array and then write the contents of array/ object in outputStream.write(); in order to write in numbers.txt file.

jnd Over a year ago

You put what you want to write as the arguement. For example outputStream.write("hello"); or outputStream.write(15);

Newbie Over a year ago

#jnd I think you didn't get my question as I am retrieving text from file#1 and writing in file#2. Its not that I want to write anything from myself inside quotes...

Newbie Over a year ago

Thanks #jnd for the reply. It is almost similar to what I wanted. I have achieved my desired my results through your code but can I ask you a question that e.g. If my program asks the user to press 1 to read from file and 2 to write to a new file and do I have to use this BufferedReader method and read the file if user press 2 or is there a way that if user has pressed 1 and the program has saved all the file contents in an array/ arraylist and when user has pressed 2 it writes everything from that array/arraylist into file#2.

jnd Over a year ago

You can do either way. You would just make your read method return an array of strings and then pass that to your write method for it to write.

|

xtra · Accepted Answer · 2018-12-21 22:08:24Z

I'd use a BufferedReader that wraps a FileReader and a BufferedWriter that wraps a FileWriter.

Since you want to do it using two different methods you have to store the data in a List<String> data to pass it between the methods.

public class ReadnWrite {

    public static List<String> readFile() throws IOException {
        try(BufferedReader br = new BufferedReader(new FileReader("original.txt"))){
            List<String> listOfData = new ArrayList<>();
            String d;
            while((d = br.readLine()) != null){
                listOfData.add(d);
            }
            return listOfData;
        }
    }

    public static void writeFile(List<String> listOfData) throws IOException{
        try(BufferedWriter bw = new BufferedWriter(new FileWriter("numbers.txt"))){
            for(String str: listOfData){
                bw.write(str);
                bw.newLine();
            }
        }
    }

    public static void main(String[] args) throws IOException {
        List<String> data = readFile();
        writeFile(data);
    }
}

As an alternative, if you don't have to do operations on the data between read and write I'd also do it in one method.

public class CopyFileBufferedRW {

    public static void main(String[] args) {
        File originalFile = new File("original.txt");
        File newFile = new File(originalFile.getParent(), "numbers.txt");

        try (BufferedReader br = new BufferedReader(new FileReader(originalFile));
             BufferedWriter bw = new BufferedWriter(new FileWriter(newFile))) {
            String s;
            while ((s = br.readLine()) != null) {
                bw.write(s);
                bw.newLine();
            }
        } catch (IOException e) {
            System.err.println("error during copying: " + e.getMessage());
        }
    }
}

Maher Abuthraa · Accepted Answer · 2017-02-14 17:09:18Z

0

Here is my way how to copy files:

BufferedReader br = null;
BufferedWriter bw = null;

try {
    br = new BufferedReader(new InputStreamReader(new FileInputStream(new File("origin.txt"))));
    bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream(new File("target.txt"))));

    int i;
    do {
        i = br.read();
        if (i != -1) {
            bw.write(i);
        }
    } while (i != -1);

} catch (IOException e) {
    System.err.println("error during copying: "+ e.getMessage());
} finally {
    try {
        if (br != null) br.close();
        if (bw != null) bw.close();
    } catch (IOException e) {
        System.err.println("error during closing: "+ e.getMessage());
    }
}

answered Feb 14, 2017 at 17:09

Maher Abuthraa

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