Java Read File to String UTF-8 - How to read file line by line in Java

Overview

In this tutorial, we show you how to read file to string with utf-8. We read a sequence of lines from a text file and output the file line by line on the console eclipse.

We discuss three different ways for reading contents from a text file. The text file is stored at C:/data/fruits.txt with following content

Cherry
  Banana  Chico fruit
Jackfruit   Kiwifruit
Orange Pineapple  Mango Apple

Use BufferedReader to read UTF-8 encoded data from a text file.

String filePath = "C:/data/fruits.txt";

StringBuilder sb = new StringBuilder();
try (BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath), "UTF8"))) {

 String cLine;
 while ((cLine = br.readLine()) != null) {
  sb.append(cLine).append("\n");
 }
} catch (IOException e) {
 e.printStackTrace();
}

System.out.println("##### Use BufferedReader to read UTF-8 encoded data from a text file");
System.out.println(sb.toString());

Reading file in JDK 7+

In JDK 1.7, we using the java.nio.file.Files class with Files.readAllBytes(Path) method to read a complete file in memory. This method returns a byte array, which can be passed to String constructor to create String out of it

String contents = null;
  try {
   contents = new String(Files.readAllBytes(Paths.get(filePath)));
  } catch (IOException e) {
   e.printStackTrace();
  }
  System.out.println("##### for JDK 7+");
  System.out.println(contents);

Reading file line by line JDK 8+

We using java.nio.file.Files.lines() method, which returns a Stream of String read from file, where bytes are converted to character using UTF-8 character encoding.

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

  System.out.println("##### for JDK 8+");
  System.out.println(stringBuilder.toString());

ReadFileToStringExample.java

package com.jackrutorial;

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

public class ReadFileToStringExample {

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

  //using BufferedReader
  StringBuilder sb = new StringBuilder();
  try (BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(filePath), "UTF8"))) {

   String cLine;
   while ((cLine = br.readLine()) != null) {
    sb.append(cLine).append("\n");
   }
  } catch (IOException e) {
   e.printStackTrace();
  }
  
  System.out.println("##### Use BufferedReader to read UTF-8 encoded data from a text file");
  System.out.println(sb.toString());
  
  //for java 7+
  String contents = null;
  try {
   contents = new String(Files.readAllBytes(Paths.get(filePath)));
  } catch (IOException e) {
   e.printStackTrace();
  }
  System.out.println("##### for JDK 7+");
  System.out.println(contents);
  
  //for java 8+
  StringBuilder stringBuilder = new StringBuilder();
  try (Stream stream = Files.lines( Paths.get(filePath), StandardCharsets.UTF_8)) 
  {
   stream.forEach(s -> stringBuilder.append(s).append("\n"));
  }
  catch (IOException e) 
  {
   e.printStackTrace();
  }

  System.out.println("##### for JDK 8+");
  System.out.println(stringBuilder.toString());
 }
}

Console Output

##### Use BufferedReader to read UTF-8 encoded data from a text file
Cherry
  Banana  Chico fruit
Jackfruit   Kiwifruit
Orange Pineapple  Mango Apple

##### for JDK 7+
Cherry
  Banana  Chico fruit
Jackfruit   Kiwifruit
Orange Pineapple  Mango Apple
##### for JDK 8+
Cherry
  Banana  Chico fruit
Jackfruit   Kiwifruit
Orange Pineapple  Mango Apple

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