How to read data from one file and print to another file in Java?

Java provides I/O Streams to read and write data where a Stream represents an input source or an output destination which could be a file, i/o devise, other programs, etc.

In general, a Stream will be an input stream or, an output stream.

  • InputStream − This is used to read data from a source.

  • OutputStream − This is used to write data to a destination.

Based on the data they handle there are two types of streams −

  • Byte Streams − These handle data in bytes (8 bits) i.e., the byte stream classes read/write data of 8 bits. Using these you can store characters, videos, audios, images, etc.

  • Character Streams − These handle data in 16 bit Unicode. Using these you can read and write text data only.

The following diagram illustrates all the input and output Streams (classes) in Java.

Among these, you can read the contents of a file using Scanner, BufferedReader and, FileReader classes.

In the same way, you can write data into a file using BufferedWriter, FileOutputStream, FileWriter.

Writing contents of one file to other

Following is a Java program that reads data from a file to a String using the Scanner class and writes it to another file using the FileWriter class.


import java.util.Scanner;
public class CopyContent {
   public static void main(String[] args) throws IOException {
      //Instantiating a file class
      File file = new File("D:\sampleData.txt");
      //Instantiate an FileInputStream class
      FileInputStream inputStream = new FileInputStream(file);
      //Instantiating the Scanner class
      Scanner sc = new Scanner(inputStream);
      //StringBuffer to store the contents
      StringBuffer buffer = new StringBuffer();
      //Appending each line to the buffer
      while(sc.hasNext()) {
         buffer.append(" "+sc.nextLine());
      System.out.println("Contents of the file: "+buffer);
      //Creating a File object to hold the destination file
      File dest = new File("D:\outputFile.txt");
      //Instantiating an FileWriter object
      FileWriter writer = new FileWriter(dest);
      //Writing content to the destination
      System.out.println("File copied successfully.......");


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File copied successfully.......

Updated on: 10-Sep-2019

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