Java – Read File to String Examples

Learn to read file to string in java. Examples use Files.readAllBytes, Files.lines and FileReader & BufferedReader to read file content.

Quick Reference

Source code of all 3 examples for reading files into string.

//Example 1

//Read file content into string with - Files.lines(Path path, Charset cs)

private static String readLineByLineJava8(String filePath) 
{
	StringBuilder contentBuilder = new StringBuilder();
	try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) 
	{
		stream.forEach(s -> contentBuilder.append(s).append("\n"));
	}
	catch (IOException e) 
	{
		e.printStackTrace();
	}
	return contentBuilder.toString();
}

//Example 2

//Read file content into string with - Files.readAllBytes(Path path)

private static String readAllBytesJava7(String filePath) 
{
	String content = "";
	try 
	{
		content = new String ( Files.readAllBytes( Paths.get(filePath) ) );
	} 
	catch (IOException e) 
	{
		e.printStackTrace();
	}
	return content;
}

//Example 3

//Read file content into string with - using BufferedReader and FileReader
//You can use this if you are still not using Java 8

private static String usingBufferedReader(String filePath) 
{
	StringBuilder contentBuilder = new StringBuilder();
	try (BufferedReader br = new BufferedReader(new FileReader(filePath))) 
	{

		String sCurrentLine;
		while ((sCurrentLine = br.readLine()) != null) 
		{
			contentBuilder.append(sCurrentLine).append("\n");
		}
	} 
	catch (IOException e) 
	{
		e.printStackTrace();
	}
	return contentBuilder.toString();
}

I have placed a file data.txt at location c:/temp. I will read this file in all 3 examples.

File content in c:/temp/data.txt

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Learn to grow.

Read File to String using Files.lines() [≥ Java 8]

lines() method read all lines from a file to stream and populates lazily as the stream is consumed. Bytes from the file are decoded into characters using the specified charset.

import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.stream.Stream;

public class ReadFileToString 
{
	public static void main(String[] args) 
	{
		String filePath = "c:/temp/data.txt";

		System.out.println( readLineByLineJava8( filePath ) );
	}


	//Read file content into string with - Files.lines(Path path, Charset cs)

	private static String readLineByLineJava8(String filePath) 
	{
		StringBuilder contentBuilder = new StringBuilder();

		try (Stream<String> stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) 
		{
			stream.forEach(s -> contentBuilder.append(s).append("\n"));
		}
		catch (IOException e) 
		{
			e.printStackTrace();
		}

		return contentBuilder.toString();
	}
}

Output:

welcome to howtodoinjava.com blog. 
Learn to grow.

Read File to String using Files.readAllBytes() [≥ Java 7]

readAllBytes() method reads all the bytes from a file. The method ensures that the file is closed when all bytes have been read or an I/O error, or other runtime exception, is thrown.

After reading all bytes, we pass those bytes to String class constructor to create a string.

import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Paths;

public class ReadFileToString 
{
	public static void main(String[] args) 
	{
		String filePath = "c:/temp/data.txt";

		System.out.println( readAllBytesJava7( filePath ) );
	}

	//Read file content into string with - Files.readAllBytes(Path path)

	private static String readAllBytesJava7(String filePath) 
	{
		String content = "";

		try 
		{
			content = new String ( Files.readAllBytes( Paths.get(filePath) ) );
		} 
		catch (IOException e) 
		{
			e.printStackTrace();
		}

		return content;
	}
}

Output:

welcome to howtodoinjava.com blog. 
Learn to grow.

Read File to String using BufferedReader [< Java 7]

If you are still not using java 7 or later, then use BufferedReader class. It’s readLine() method reads the file one line at a time and return the content.

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class ReadFileToString 
{
	public static void main(String[] args) 
	{
		String filePath = "c:/temp/data.txt";

		System.out.println( usingBufferedReader( filePath ) );
	}

	//Read file content into string with - using BufferedReader and FileReader
	//You can use this if you are still not using Java 8

	private static String usingBufferedReader(String filePath) 
	{
		StringBuilder contentBuilder = new StringBuilder();
		try (BufferedReader br = new BufferedReader(new FileReader(filePath))) 
		{

			String sCurrentLine;
			while ((sCurrentLine = br.readLine()) != null) 
			{
				contentBuilder.append(sCurrentLine).append("\n");
			}
		} 
		catch (IOException e) 
		{
			e.printStackTrace();
		}
		return contentBuilder.toString();
	}
}

Output:

welcome to howtodoinjava.com blog. 
Learn to grow.

Use any of above given methods to read file into string using java.

Happy Learning !!