The main logic of copying a file is to read the file associated with FileInputStream variable and write the read contents into the file associated with FileOutputStream variable. We can copy a file from one location to another using FileInputStream and FileOutputStream classes in Java. Now before adhering forward let us discuss essential methods that will be used in the program.
Method 1: read(): Reads a byte of data. Present in FileInputStream.
Return type: An integer value
Syntax: Other versions
int read(byte[] bytearray or int read(byte[] bytearray, int offset, int length)
Method 2: write(int b): Writes a byte of data. Present in FileOutputStream
Syntax:
void write(byte[] bytearray) or void write(byte[] bytearray, int offset, int length)
Implementation: We will be creating two files named “demo.rtf” and “outputdemo.rtf” as another file where no content is there. Below is an image of the “demo.rtf” file as a sample input image.
- First, we will create two objects of the File class, one referring to FileInputClass and the other for FileOutputStream Class.
- Now we will create objects of FileInputStream class and FileOutputStream class prior to creating variables and assigning null to corresponding datatypes.
- Pass respective objects of FileInputStream and FileOutputStream objects
- Now using loops keep reading from a file and write it to another file using FileOuputStream using the read() and write() methods.
Tip: It is good practice to close the streams to avoid memory leakage.
Example 1:
Java
// Java Program to Illustrate File InputStream and File// Importing required classesimport java.io.File;import java.io.FileInputStream;import java.io.FileNotFoundException;import java.io.FileOutputStream;// Main classclass GFG { // Main driver method public static void main(String[] args) { // Creating object of File class // Passing files from directory of local machine File file = new File( "/Users/mayanksolanki/Desktop/demo.rtf"); File oFile = new File( "/Users/mayanksolanki/Desktop/outputdemo.rtf"); // Now creating object of FileInputStream // Here they are variables FileInputStream fis = null; FileOutputStream fos = null; try { // Now we make them as objects of both classes // and passed reference of file in directory fis = new FileInputStream(file); fos = new FileOutputStream(oFile); } // Catch block to handle exceptions catch (FileNotFoundException e) { // Display message if exception occurs // File Not Found or Path is Incorrect System.out.println(e.printStackTrace()); } try { // Now let us check how many bytes are available // inside content of file fis.available(); } catch (Exception e) { e.printStackTrace(); } // Using while loop to // write over outputdemo file int i = 0; while (i = fis.read() != -1) { fos.write(i); } // It will execute no matter what // to close connections which is // always good practice finally { // Closing the file connections // For input stream if (fis != null😉 { fis.clsoe(); } // For output stream if (fos != null) { fos.close(); } } }} |
Output: The same content will be reflected back in the “outputdemo.rtf” file as seen below in the “demo.rtf” file.
Example 2:
Java
// Java Program Illustrating Copying a src File// to Destination// Importing required classesimport java.io.*;// Main class// src2destclass GFG { // Main driver method public static void main(String args[]) throws FileNotFoundException, IOException { // If file doesnot exist FileInputStream throws // FileNotFoundException and read() write() throws // IOException if I/O error occurs FileInputStream fis = new FileInputStream(args[0]); // Assuming that the file exists and // need not to be checked FileOutputStream fos = new FileOutputStream(args[1]); int b; while ((b = fis.read()) != -1) fos.write(b); // read() method will read only next int so we used // while loop here in order to read upto end of file // and keep writing the read int into dest file fis.close(); fos.close(); }} |
Output:
Output Explanation: The name of the src file and dest file must be provided using command line arguments where args[0] is the name of the source file and args[1] is the name of the destination file.
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