Read String line by line

Question

Given a string that isn't too long, what is the best way to read it line by line?

I know you can do:

BufferedReader reader = new BufferedReader(new StringReader());
reader.readLine();

Another way would be to take the substring on the eol:

final String eol = System.getProperty("line.separator");
output = output.substring(output.indexOf(eol + 1));

Any other maybe simpler ways of doing it? I have no problems with the above approaches, just interested to know if any of you know something that may look simpler and more efficient?

user_125844 · Answer

There is also Scanner. You can use it just like the BufferedReader:

Scanner scanner = new Scanner(myString);
while (scanner.hasNextLine()) {
  String line = scanner.nextLine();
  // process the line
}
scanner.close();

I think that this is a bit cleaner approach that both of the suggested ones.

user_98596 · Answer

You can also use the split method of String:

String[] lines = myString.split(System.getProperty("line.separator"));

This gives you all lines in a handy array.

I don't know about the performance of split. It uses regular expressions.

Brian_Agnew_12960 · Answer

Using Apache Commons IOUtils you can do this nicely via

List lines = IOUtils.readLines(new StringReader(string));

It's not doing anything clever, but it's nice and compact. It'll handle streams as well, and you can get a LineIterator too if you prefer.

user_1514467 · Answer

The easiest and most universal approach would be to just use the regex Linebreak matcher \R which matches Any Unicode linebreak sequence:

Pattern NEWLINE = Pattern.compile("\R")
String lines[] = NEWLINE.split(input)

@see https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/util/regex/Pattern.html

Read String line by line

11 Answers