How to write to file in Java – BufferedWriter

In Java, we can use BufferedWriter to write content into a file.

	// jdk 7
	try (FileWriter writer = new FileWriter("app.log");
		 BufferedWriter bw = new BufferedWriter(writer)) {

		bw.write(content);

	} catch (IOException e) {
		System.err.format("IOException: %s%n", e);
	}

Note

If possible, uses Files.write instead, one line, simple and nice.

Read Files.write examples

    List<String> list = Arrays.asList("Line 1", "Line 2");
    Files.write(Paths.get("app.log"), list);

1. BufferedWriter

Write content into a file.
WriteFileBufferedWriter1.java

package com.favtuts.io.file;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class WriteFileBufferedWriter1 {

    public static void main(String[] args) {
        
        String content = "This is the content to write into file\n";

        // If the file doesn't exists, create and write to it
        // If the file exists, truncate (remove all content) and write to it
        try (FileWriter writer = new FileWriter("app.log");
            BufferedWriter bw = new BufferedWriter(writer)
        ) {

            bw.write(content);
            
        } catch (IOException e) {
            System.err.format("IOException: %s%n", e);
        }
    }
    
}

Output:

app.log

This is the content to write into file

For Append mode, pass a true as second argument in FileWriter

	// If the file exists, append to it
	try (FileWriter writer = new FileWriter("app.log", true);
		 BufferedWriter bw = new BufferedWriter(writer)) {

		bw.write(content);

	} catch (IOException e) {
		System.err.format("IOException: %s%n", e);
	}

2. BufferedWriter (Old School Style)

Before the JDK 7 try-resources, we need to handle the close() manually. A painful memory, let see this :

WriteFileBufferedWriter2.java

package com.favtuts.io.file;

import java.io.BufferedWriter;
import java.io.FileWriter;
import java.io.IOException;

public class WriteFileBufferedWriter {

    public static void main(String[] args) {
        
        writeFileBufferedWriterClassic();
    }

    private static void writeFileBufferedWriterClassic() {
        BufferedWriter bw = null;
        FileWriter fw = null;

        try {

            String content = "This is the content to write into file\n";

            fw = new FileWriter("app.log");
            //fw = new FileWriter("app.log", true);  Append mode
            bw = new BufferedWriter(fw);
            bw.write(content);

        } catch (IOException e) {
            System.err.format("IOException: %s%n", e);
        } finally {
            try {
                if (bw != null)
                    bw.close();

                if (fw != null)
                    fw.close();
            } catch (IOException ex) {
                System.err.format("IOException: %s%n", ex);
            }
        }
    }
}

Output

app.log

This is the content to write into file

Download Source Code

$ git clone https://github.com/favtuts/java-core-tutorials-examples

$ cd java-io/file

References

• Java – How to create and write to a file
• Java Tutorials – Reading, Writing, and Creating Files
• Files JavaDocs