Java - Writing to File

Write To File in Java

We can write to a file in Java using multiple ways. Following are three most popular ways to create a file in Java −

• Using FileOutputStream() constructor

• Using FileWriter.write() method

• Using Files.write() method

Let's take a look at each of the way to write file in Java.

Write To File Using FileOutputStream Constructor

FileOutputStream is used to create a file and write data into it. The stream would create a file, if it doesn't already exist, before opening it for output.

Here are two constructors which can be used to create a FileOutputStream object.

Syntax

Following constructor takes a file name as a string to create an output stream object to write the file −

OutputStream f = new FileOutputStream("C:/java/hello.txt") 

Syntax

Following constructor takes a file object to create an output stream object to write the file. First, we create a file object using File() method then we're writing bytes to the stream as follows −

File f = new File("C:/java/hello.txt");
OutputStream f = new FileOutputStream(f);

for(int x = 0; x < bWrite.length ; x++) {
   os.write( bWrite[x] );   // writes the bytes
}

Example: Write To File Using FileOutputStream Constructor

Following is the example to demonstrate FileOutputStream to write a file in current directory −

package com.tutorialspoint;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

public class FileTest {

   public static void main(String args[]) {
   
      try {
         byte bWrite [] = {65, 66, 67, 68, 69};
         OutputStream os = new FileOutputStream("test.txt");
         for(int x = 0; x < bWrite.length ; x++) {
            os.write( bWrite[x] );   // writes the bytes
         }
         os.close();
     
         InputStream is = new FileInputStream("test.txt");
         int size = is.available();

         for(int i = 0; i < size; i++) {
            System.out.print((char)is.read() + "  ");
         }
         is.close();
      } catch (IOException e) {
         System.out.print("Exception");
      }	
   }
}

The above code would create file test.txt and would write given numbers in binary format. Same would be the output on the stdout screen.

Output

A  B  C  D  E  

Write To File Using FileWriter.write() Method

FileWriter.write() method of FileWriter class allows to write chars to a file as shown below −

Syntax

// get an existing file
File file = new File("d://test//testFile1.txt");

// Write Content
FileWriter writer = new FileWriter(file);
writer.write("Test data");
writer.close();

Example: Write To File Using FileWriter.write() Method

Following is the example to demonstrate File to write to a file in given directory using FileWriter.write() method −

package com.tutorialspoint;

import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

public class FileTest {

   public static void main(String args[]) {
   
      try {
          File file = new File("d://test//testFile1.txt");
          
          //Create the file
          if (file.createNewFile()) { 
             System.out.println("File is created!");
          } else {
             System.out.println("File already exists.");
          } 
          
          // Write Content
          FileWriter writer = new FileWriter(file);
          writer.write("Test data");
          writer.close();
          
          
          // read content
          FileReader reader = new FileReader(file);
          
          int c;
          while ((c = reader.read()) != -1) {
        	  char ch = (char) c;
              System.out.print(ch);
          }
      } catch (IOException e) {
         System.out.print("Exception");
      }	
   }
}

The above code would create file test.txt and would write given string in text format. Same would be the output on the stdout screen.

Output

File is created!
Test data

Write To File Using Files.write() Method

Files.write() is a newer and more flexible method create a file and write content to a file in same command as shown below −

Syntax

String data = "Test data";
Files.write(Paths.get("d://test/testFile3.txt"), data.getBytes());

List<String> lines = Arrays.asList("1st line", "2nd line");
Files.write(Paths.get("file6.txt"), lines, StandardCharsets.UTF_8, 
   StandardOpenOption.CREATE, StandardOpenOption.APPEND);

Example: Write To File Using Files.write() Method

Following is the example to demonstrate File to create a file in given directory using Files.write() method −

package com.tutorialspoint;

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.util.Arrays;
import java.util.List;

public class FileTest {

   public static void main(String args[]) {
   
      try {
    	  String data = "Test data";
          Files.write(Paths.get("d://test/testFile3.txt"), data.getBytes());
          List<String> lines = Arrays.asList("1st line", "2nd line");
          Files.write(Paths.get(
             "file6.txt"), lines, StandardCharsets.UTF_8, 
             StandardOpenOption.CREATE, StandardOpenOption.APPEND);
          
          List<String> content = Files.readAllLines(Paths.get("d://test/testFile3.txt"));

          System.out.println(content);
          
          content = Files.readAllLines(Paths.get("file6.txt"));

          System.out.println(content);
      } catch (IOException e) {
         System.out.print("Exception");
      }	
   }
}

The above code would create file test.txt and would write given strings in text format. Same would be the output on the stdout screen.

Output

[Test data]
[1st line, 2nd line]