Check if string contains \n Java

Question

How do I check if string contains \\n or new line character ?

word.contains(\"\\\\n\")
word.contains(\"\\n\")

Answer 1

If the string was constructed in the same program, I would recommend using this:

String newline = System.getProperty("line.separator");
boolean hasNewline = word.contains(newline);

But if you are specced to use \n, this driver illustrates what to do:

class NewLineTest {
    public static void main(String[] args) {
        String hasNewline = "this has a newline\n.";
        String noNewline = "this doesn't";

        System.out.println(hasNewline.contains("\n"));
        System.out.println(hasNewline.contains("\\n"));
        System.out.println(noNewline.contains("\n"));
        System.out.println(noNewline.contains("\\n"));

    }

}

Resulted in

true
false
false
false

In reponse to your comment:

class NewLineTest {
    public static void main(String[] args) {
        String word = "test\n.";
        System.out.println(word.length());
        System.out.println(word);
        word = word.replace("\n","\n ");
        System.out.println(word.length());
        System.out.println(word);

    }

}

Results in

6
test
.
7
test
 .

Answer 2

For portability, you really should do something like this:

public static final String NEW_LINE = System.getProperty("line.separator")
.
.
.
word.contains(NEW_LINE);

unless you're absolutely certain that "\n" is what you want.

Answer 3

The second one:

word.contains("\n");

Answer 4

I'd rather trust JDK over System property. Following is a working snippet.

    private boolean checkIfStringContainsNewLineCharacters(String str){
        if(!StringUtils.isEmpty(str)){
            Scanner scanner = new Scanner(str);
            scanner.nextLine();
            boolean hasNextLine =  scanner.hasNextLine();
            scanner.close();
            return hasNextLine;
        }
        return false;
    }