How to read a UTF-8 file in Java

In Java, the InputStreamReader accepts a charset to decode the byte streams into character streams. We can pass a StandardCharsets.UTF_8 into the InputStreamReader constructor to read data from a UTF-8 file.

import java.nio.charset.StandardCharsets;

  //...
  try (FileInputStream fis = new FileInputStream(file);
       InputStreamReader isr = new InputStreamReader(fis, StandardCharsets.UTF_8);
       BufferedReader reader = new BufferedReader(isr)
  ) {

      String str;
      while ((str = reader.readLine()) != null) {
          System.out.println(str);
      }

  } catch (IOException e) {
      e.printStackTrace();
  }

In Java 7+, many file read APIs start to accept charset as an argument, making reading a UTF-8 very easy.

  // Java 7
  BufferedReader reader = Files.newBufferedReader(path, StandardCharsets.UTF_8);

  // Java 8
  List<String> list = Files.readAllLines(path, StandardCharsets.UTF_8);

  // Java 8
  Stream<String> lines = Files.lines(path, StandardCharsets.UTF_8);

  // Java 11
  String s = Files.readString(path, StandardCharsets.UTF_8);

1. UTF-8 File

A UTF-8 encoded file c:\\temp\\test.txt, with Chinese characters.

2. Read UTF-8 file

This example shows a few ways to read a UTF-8 file.

package com.mkyong.io.howto;

import java.io.*;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.stream.Stream;

public class UnicodeRead {

    public static void main(String[] args) {

        String fileName = "c:\\temp\\test.txt";

        //readUnicodeJava11(fileName);
        readUnicodeBufferedReader(fileName);
        //readUnicodeFiles(fileName);
        //readUnicodeClassic(fileName);

    }

    // Java 7 - Files.newBufferedReader(path, StandardCharsets.UTF_8)
    // Java 8 - Files.newBufferedReader(path) // default UTF-8
    public static void readUnicodeBufferedReader(String fileName) {

        Path path = Paths.get(fileName);

        // Java 8, default UTF-8
        try (BufferedReader reader = Files.newBufferedReader(path)) {

            String str;
            while ((str = reader.readLine()) != null) {
                System.out.println(str);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static void readUnicodeFiles(String fileName) {

        Path path = Paths.get(fileName);
        try {

            // Java 11
            String s = Files.readString(path, StandardCharsets.UTF_8);
            System.out.println(s);

            // Java 8
            List<String> list = Files.readAllLines(path, StandardCharsets.UTF_8);
            list.forEach(System.out::println);

            // Java 8
            Stream<String> lines = Files.lines(path, StandardCharsets.UTF_8);
            lines.forEach(System.out::println);

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    // Java 11, adds charset to FileReader
    public static void readUnicodeJava11(String fileName) {

        Path path = Paths.get(fileName);

        try (FileReader fr = new FileReader(fileName, StandardCharsets.UTF_8);
             BufferedReader reader = new BufferedReader(fr)) {

            String str;
            while ((str = reader.readLine()) != null) {
                System.out.println(str);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static void readUnicodeClassic(String fileName) {

        File file = new File(fileName);

        try (FileInputStream fis = new FileInputStream(file);
             InputStreamReader isr = new InputStreamReader(fis, StandardCharsets.UTF_8);
             BufferedReader reader = new BufferedReader(isr)
        ) {

            String str;
            while ((str = reader.readLine()) != null) {
                System.out.println(str);
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

    }
}

Output

line 1
line 2
line 3
你好，世界

Download Source Code

References

• FileWriter JavaDoc
• BufferedWriter JavaDoc
• InputStreamReader JavaDoc
• Wikipedia – UTF-8
• Charset JavaDoc