How to get start position and end position of line in a string

Question

I have a text with multiple lines and i have the line number as an input now i'd like to have the start position and end position of that line, here is what i already did but it's not working:

        private int[] getPos(int line) {
            String[] lines = textArea.getText().split(System.getProperty("line.separator"));
            int i=0;
            int pos = 0;
            while( i < lines.length){
                if(i==line)
                    break;
                pos = pos+lines[i].length();

                i++;
            }

            int[] s = {pos,pos+lines[i].length()};
            return s;
        }

example of text:

line1
line2
line3

i want to use the result to highlight the line:

textArea.getHighlighter().addHighlight(startPos, endPos,highlightPainter);

Answer 1

jText.getText().indexOf( lines[i] )

This will give you the start position. Add the line length to that and you have the end.

Cheers

EDIT: If there are duplicated lines, you may have to tweak the code a bit to either get the first or last line it finds.

Answer 2

If you want to extract the first instance of the substring (or are sure that there will be only one), you can use the .indexOf(String str) method:

String foo = "foo bar";
String toLookUp = "bar";
int initialPosition = foo.indexOf(toLookUp);
System.out.println("Initial Position: " + initialPosition + " end: " + initialPosition + toLookUp.length);

Alternatively:

String foo = "foo bar bar";
String toLookUp = "bar";
int initialPosition = foo.indexOf(toLookUp);
while(initialPosition != -1)
{
     System.out.println("Initial Position: " + initialPosition + " end: " + initialPosition + toLookUp.length);
     initialPosition = foo.indexOf(toLookUp, initialPosition + toLookUp.length;
}

Answer 3

Because your lines counter start from '1' and your array counter start from '0' you get wrong output.

You need need to add line -= 1; after int pos = 0; and you get correct output.