Java - How to read a Text file

javaio

There are various ways to read a Text file.

  • BufferedReader
  • Files
  • commons-io의 FileUtil

Let`s see how to read a text file through an example.

Read text file using BufferedReader

You can read text files using BufferedReader. Just pass the FileReader object as an argument to the constructor of BufferedReader.

You can read the text.txt file and output the text like this:

File file = new File("/home/js/test/text.txt");
try (BufferedReader br = new BufferedReader(new FileReader(file))) {
    String line;
    while ((line = br.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

readLine() returns null if there is no more to read.

Running it, the result is:

Chicago – April 28, 2020 Society for Incentive Travel Excellence (SITE) will hold its third Covid-19 related webinar Friday, May 1, at 10AM (Chicago) 4PM (London) 11PM (Singapore).
With previous webinars having attracted a cumulative audience of over 700 incentive travel professionals, we now turn our attention to Health Security in a Post Covid-19 World.

Reading text files using Files

You can read and print text files using Files.

The following code outputs the contents of text.txt. readAllLines() returns a list of strings of files.

try {
    Path path = Paths.get("/home/js/test/text.txt");
    List<String> lines = Files.readAllLines(path);
    for(String line : lines) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

If you want to use Files and BufferedReader, you can also implement it like this:

Path path = Paths.get("/home/js/test/text.txt");
try (BufferedReader reader = Files.newBufferedReader(path)) {
    String line;
    while ((line = reader.readLine()) != null) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

(newBufferedReader() seems to be available since Java8.)

result

Chicago – April 28, 2020 Society for Incentive Travel Excellence (SITE) will hold its third Covid-19 related webinar Friday, May 1, at 10AM (Chicago) 4PM (London) 11PM (Singapore).
With previous webinars having attracted a cumulative audience of over 700 incentive travel professionals, we now turn our attention to Health Security in a Post Covid-19 World.

Read text file using commons-io library

You can also read files using the commons-io library.

Gradle project adds the following to dependencies of build.gradle.

dependencies {
  compile group: 'commons-io', name: 'commons-io', version: '2.6'
  ...
}

For projects that use other build systems such as Maven, refer to mvnrepository.com and configure it.

The following is the code to read a file using FileUtils of commons-io. readLines() takes an encoding type as an argument. And it returns a list of strings.

try {
    File file = new File("/home/js/test/text.txt");
    List<String> lines = FileUtils.readLines(file, "UTF-8");
    for(String line : lines) {
        System.out.println(line);
    }
} catch (IOException e) {
    e.printStackTrace();
}

If List If you dont need to receive it as , and you can return a String object with all the texts combined, you can use readFileToString()`.

System.out.println();
try {
    File file = new File("/home/js/test/text.txt");
    String strings = FileUtils.readFileToString(file, "UTF-8");
    System.out.println(strings);
} catch (IOException e) {
    e.printStackTrace();
}

The execution result is the same as the above codes. just concatenated into one string. (concatenated)

result

Chicago – April 28, 2020 Society for Incentive Travel Excellence (SITE) will hold its third Covid-19 related webinar Friday, May 1, at 10AM (Chicago) 4PM (London) 11PM (Singapore).
With previous webinars having attracted a cumulative audience of over 700 incentive travel professionals, we now turn our attention to Health Security in a Post Covid-19 World.

Reference

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