Count the number of lines in a Java String

Question

Need some compact code for counting the number of lines in a string in Java. The string is to be separated by \r or \n. Each instance of those newline characters will be considered as a separate line. For example,

"Hello\nWorld\nThis\nIs\t"

should return 4. The prototype is

private static int countLines(String str) {...}

Can someone provide a compact set of statements? I have solution at here but it is too long, I think. Thank you.

Answer 1

There has been a similar question to yours here. Hope it helps.

Answer 2

"Hello\nWorld\nthis\nIs\t".split("[\n\r]").length

You could also do

"Hello\nWorld\nthis\nis".split(System.getProperty("line.separator")).length to use the systems default line separator character(s).

Answer 3

I suggest you look for something like this

String s; 
s.split("\n\r");

Look for the instructions here for Java's String Split method

If you have any problem, post your code

Answer 4

private static int countLines(String str){
   String[] lines = str.split("\r\n|\r|\n");
   return  lines.length;
}

Answer 5

If you have the lines from the file already in a string, you could do this:

int len = txt.split(System.getProperty("line.separator")).length;

EDIT:

Just in case you ever need to read the contents from a file (I know you said you didn't, but this is for future reference), I recommend using Apache Commons to read the file contents into a string. It's a great library and has many other useful methods. Here's a simple example:

import org.apache.commons.io.FileUtils;

int getNumLinesInFile(String file) {

    String content = FileUtils.readFileToString(file);
    return content.split(System.getProperty("line.separator")).length;
}

Answer 6

How about this:

String yourInput = "...";
Matcher m = Pattern.compile("\n|\r").matcher(yourInput);
int lines = 1;
while (m.find())
{
    lines ++;
}

On this way you don't need to split and no new String objects will be created (what happens by String.split(String);).

Answer 7

Well, this is a solution using no "magic" regexes, or other complex sdk features.

Obviously, the regex matcher is probably better to use in real life, as its quicker to write. (And it is probably bug free too...)

On the other hand, You should be able to understand whats going on here...

If you want to handle the case \r\n as a single new-line (msdos-convention) you have to add your own code. Hint, you need another variable that keeps track of the previous character matched...

int lines= 1;

for( int pos = 0; pos < yourInput.length(); pos++){
    char c = yourInput.charAt(pos);
    if( c == "\r" || c== "\n" ) {
        lines++;
    }
}

Answer 8

new StringTokenizer(str, "\r\n").countTokens();

Note that this will not count empty lines (\n\n).

CRLF (\r\n) counts as single line break.