This post shows various options to write to a file in Java.
In Java there are two classes FileWriter and FileOutputStream for writing to a file. Out of these two FileWriter is meant for writing streams of characters and FileOutputStream is used for writing streams of raw bytes.
In general, a Writer sends its output immediately to the underlying character or byte stream. Unless prompt output is required, it is advisable to wrap a BufferedWriter around any Writer whose write() operations may be costly, such as FileWriters and OutputStreamWriters.
So the classes you should use for writing to a file in Java are BufferedWriter and BufferedOutputStream.
- Refer How to Read File in Java to see different options available for reading a file in Java.
Apart from these classes Files class added in Java 7 also provides methods for writing to a file in Java. There is Files.write() method to write bytes to a file. There is also a Files.newBufferedWriter() method which returns a BufferedWriter that may be used to write text to the file in an efficient manner.
So there are four options for writing to a file in Java-
- Using BufferedWriter
- Using BufferedOutputStream
- Using Files.write() method
- Using Files.newBufferedWriter() method
Java program to write to a file using BufferedWriter
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import java.io.BufferedWriter; import java.io.FileWriter; import java.io.IOException; public class WriteToFile { public static void main(String[] args) { writeFile("D:\\test.txt"); } private static void writeFile(String fileName){ BufferedWriter bw = null; try { // wrapping FileWriter instance bw = new BufferedWriter(new FileWriter(fileName)); bw.write("This is a test line"); bw.newLine(); bw.write("Line written by Java program in knpCode.com"); }catch (IOException exp){ exp.printStackTrace(); }finally{ if(bw != null){ try { bw.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } } |
Java program to write to a file using BufferedOutputStream
If you have to write raw bytes then you can use BufferedOutputStream class. In the example code getBytes() method is used to encode string into bytes.
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import java.io.BufferedOutputStream; import java.io.FileOutputStream; import java.io.IOException; public class WriteToFile { public static void main(String[] args) { writeFile("D:\\test.txt"); } private static void writeFile(String fileName){ BufferedOutputStream bw = null; try { bw = new BufferedOutputStream(new FileOutputStream(fileName)); // may have to use \r\n for Windows OS bw.write("This is a test line\n".getBytes()); bw.write("Line written by Java program in knpCode.com".getBytes()); }catch (IOException exp){ exp.printStackTrace(); }finally{ if(bw != null){ try { bw.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } } |
Java program to write to a file using Files.write() method
This method Writes bytes to a file so the content has to be passed as byte array.
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import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; public class WriteToFile { public static void main(String[] args) { String content = "This is a test line.\nLine written by Java program in knpCode.com."; try { Files.write(Paths.get("D:\\test.txt"), content.getBytes()); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } |
Java program to write to a file using Files.newBufferedWriter() method
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public class WriteToFile { public static void main(String[] args) { BufferedWriter bw = null; String content = "This is a test line.\nLine written by Java program in knpCode.com."; try { bw = Files.newBufferedWriter(Paths.get("D:\\test.txt")); bw.write(content); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); }finally{ if(bw != null){ try { bw.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } } |
In Java 7 you can also use try-with-resources to close the resources automatically rather than closing them explicitly using finally block.
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import java.io.BufferedWriter; import java.io.IOException; import java.nio.file.Files; import java.nio.file.Paths; public class WriteToFile { public static void main(String[] args) { String content = "This is a test line.\nLine written by Java program in knpCode.com."; try (BufferedWriter bw = Files.newBufferedWriter(Paths.get("D:\\test.txt"))) { bw.write(content); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } |
That’s all for the topic How to Write to a File in Java. If something is missing or you have something to share about the topic please write a comment.
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