Split Java String by New Line

Question

I'm trying to split text in a JTextArea using a regex to split the String by \n However, this does not work and I also tried by \r\n|\r|n and many other combination of regexes. Code:

public void insertUpdate(DocumentEvent e) {
    String split[], docStr = null;
    Document textAreaDoc = (Document)e.getDocument();

    try {
        docStr = textAreaDoc.getText(textAreaDoc.getStartPosition().getOffset(), textAreaDoc.getEndPosition().getOffset());
    } catch (BadLocationException e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }

    split = docStr.split("\\n");
}

Answer 1

A new method lines has been introduced to String class in java-11, which returns Stream<String>

Returns a stream of substrings extracted from this string partitioned by line terminators.

Line terminators recognized are line feed "\n" (U+000A), carriage return "\r" (U+000D) and a carriage return followed immediately by a line feed "\r\n" (U+000D U+000A).

Here are a few examples:

jshell> "lorem \n ipusm \n sit".lines().forEach(System.out::println)
lorem
 ipusm
 sit

jshell> "lorem \n ipusm \r  sit".lines().forEach(System.out::println)
lorem
 ipusm
  sit

jshell> "lorem \n ipusm \r\n  sit".lines().forEach(System.out::println)
lorem
 ipusm
  sit

String#lines()

Answer 2

There are three different conventions (it could be said that those are de facto standards) to set and display a line break:

• carriage return + line feed
• line feed
• carriage return

In some text editors, it is possible to exchange one for the other:

The simplest thing is to normalize to line feedand then split.

final String[] lines = contents.replace("\r\n", "\n")
                               .replace("\r", "\n")
                               .split("\n", -1);

Answer 3

In JDK11 the String class has a lines() method:

Returning a stream of lines extracted from this string, separated by line terminators.

Further, the documentation goes on to say:

A line terminator is one of the following: a line feed character "\n" (U+000A), a carriage return character "\r" (U+000D), or a carriage return followed immediately by a line feed "\r\n" (U+000D U+000A). A line is either a sequence of zero or more characters followed by a line terminator, or it is a sequence of one or more characters followed by the end of the string. A line does not include the line terminator.

With this one can simply do:

Stream<String> stream = str.lines();

then if you want an array:

String[] array = str.lines().toArray(String[]::new);

Given this method returns a Stream it upon up a lot of options for you as it enables one to write concise and declarative expression of possibly-parallel operations.

Answer 4

If, for some reason, you don't want to use String.split (for example, because of regular expressions) and you want to use functional programming on Java 8 or newer:

List<String> lines = new BufferedReader(new StringReader(string))
        .lines()
        .collect(Collectors.toList());

Answer 5

There is new boy in the town, so you need not to deal with all above complexities. From JDK 11 onward, just need to write as single line of code, it will split lines and returns you Stream of String.

public class MyClass {
public static void main(String args[]) {
   Stream<String> lines="foo \n bar \n baz".lines();
   //Do whatever you want to do with lines
}}

Some references. https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#lines() https://www.azul.com/90-new-features-and-apis-in-jdk-11/

I hope this will be helpful to someone. Happy coding.

Answer 6

The above code doesnt actually do anything visible - it just calcualtes then dumps the calculation. Is it the code you used, or just an example for this question?

try doing textAreaDoc.insertString(int, String, AttributeSet) at the end?