Java reading a file into an ArrayList?

Question

How do you read the contents of a file into an ArrayList<String> in Java?

Here are the file contents:

cat
house
dog
.
.
.

Just read each word into the ArrayList.

Answer 1

Here's a solution that has worked pretty well for me:

List<String> lines = Arrays.asList(
    new Scanner(new File(file)).useDelimiter("\\Z").next().split("\\r?\\n")
);

If you don't want empty lines, you can also do:

List<String> lines = Arrays.asList(
    new Scanner(new File(file)).useDelimiter("\\Z").next().split("[\\r\\n]+")
);

Answer 2

You can use:

List<String> list = Files.readAllLines(new File("input.txt").toPath(), Charset.defaultCharset() );

Source: Java API 7.0

Answer 3

This java code reads in each word and puts it into the ArrayList:

Scanner s = new Scanner(new File("filepath"));
ArrayList<String> list = new ArrayList<String>();
while (s.hasNext()){
    list.add(s.next());
}
s.close();

Use s.hasNextLine() and s.nextLine() if you want to read in line by line instead of word by word.

Answer 4

A one-liner with commons-io:

List<String> lines = FileUtils.readLines(new File("/path/to/file.txt"), "utf-8");

The same with guava:

List<String> lines = 
     Files.readLines(new File("/path/to/file.txt"), Charset.forName("utf-8"));

Answer 5

You can for example do this in this way (full code with exceptions handlig):

BufferedReader in = null;
List<String> myList = new ArrayList<String>();
try {   
    in = new BufferedReader(new FileReader("myfile.txt"));
    String str;
    while ((str = in.readLine()) != null) {
        myList.add(str);
    }
} catch (FileNotFoundException e) {
    e.printStackTrace();
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (in != null) {
        in.close();
    }
}

Answer 6

//CS124 HW6 Wikipedia Relation Extraction
//Alan Joyce (ajoyce)
public List<String> addWives(String fileName) {
    List<String> wives = new ArrayList<String>();
    try {
        BufferedReader input = new BufferedReader(new FileReader(fileName));
        // for each line
        for(String line = input.readLine(); line != null; line = input.readLine()) {
            wives.add(line);
        }
        input.close();
    } catch(IOException e) {
        e.printStackTrace();
        System.exit(1);
        return null;
    }
    return wives;
}