Identifying a line feed in a String

[Manju Krishna]

Hello,

I have a XML file which I parse and write the value of the node to a String. The XML tag is like,

<description>Search - Query Tab
Hide the Query Tab</description>

When I write this to a String I need to identify if there is any line feed in the given String and replace it with hard coded "\n" in it. (NOTE : Only if there is a line feed in it)
I tried to Pattern match to identify if there are any \r or \n.

descriptionBaseTerm is the <description> tag value

  Pattern pat = Pattern.compile("\r|\n|\r\n",Pattern.MULTILINE);
                Matcher match = pat.matcher(descriptionBaseTerm);
                if(match.matches()){
                    String[] temp = descriptionBaseTerm.split("\r|\n|\r\n");
                    descriptionBaseTerm = temp[0] + "\\n" + temp[1];
                    System.out.println(descriptionBaseTerm);
                }

The if loop where I split the term using the same reg exp works fine returns the String as
"Search - Query Tab\n Hide the Query Tab". Which is the desired output.

Is there any other way to acheieve this?

Please help.
Thanks,
Manju

[Sagar Rohankar]

Well, the Pattern & Matcher is the best way, but still, How about this approach ?

Use String#split("\r|\n|\r\n") and if returned array size is greater than one, you can iterate and append the each array element.

[Manju Krishna]

I have done it the same way as you have quoted.
But I was wondering why Pattern Matcher didnt work.Also wanted to know if there are any other syntax to find line feed using Patterns.

[Sagar Rohankar]

Manju Krishna wrote: But I was wondering why Pattern Matcher didnt work.

But in your original post you say, it(P&M) works

Manju Krishna wrote: Also wanted to know if there are any other syntax to find line feed using Patterns.

I don't think so.

[Ulf Dittmer]

Matcher.matches() checks whether the entire region is matched by the regexp, not whether the pattern matches anywhere in the region; Matcher.find() does that.

[Manju Krishna]

The reg exp which I had used in String split inside the if loop worked. i.e

  String[] temp = descriptionBaseTerm.split("\r|\n|\r\n");     

match.matches() was returning false anyway

[Manju Krishna]

Hello Ulf,
i tried Matcher find.

 
               Pattern pat = Pattern.compile("\r|\n|\r\n",Pattern.MULTILINE);
                Matcher match = pat.matcher(descriptionBaseTerm);
                StringBuffer sb = new StringBuffer();
                while(match.find()){
                    match.appendReplacement(sb, "\\n");                    
                }
                match.appendTail(sb);
                System.out.println(sb.toString());

This is not appending the character "\n" to end of each finds. It just returns the given String in single line

[Rob Spoor]

Why not use String.replaceAll:

descriptionBaseTerm = descriptionBaseTerm.replaceAll("\r\n|\r|\n", "\n");

This uses Pattern and Matcher (with find(), not matches()) internally.

Hmm, not even find(), but Matcher.replaceAll. That ones does use find() internally though, in a similar way as Manju's code.

[Rob Spoor]

Manju Krishna wrote:

Pattern pat = Pattern.compile("\r|\n|\r\n",Pattern.MULTILINE);

This is not appending the character "\n" to end of each finds. It just returns the given String in single line

Pattern.MULTILINE is not the flag you are looking for. That will make sure that ^ and $ are found on each line. You want Pattern.DOTALL.

[Manju Krishna]

  
                Pattern pat = Pattern.compile("\r|\n|\r\n",Pattern.MULTILINE);
                Matcher match = pat.matcher(descriptionBaseTerm);
                StringBuffer sb = new StringBuffer();
                while(match.find()){
                    match.appendReplacement(sb, "\\\\n");                    
                }
                match.appendTail(sb);
                descriptionBaseTerm = sb.toString();
 

This piece of code works..
Thanks everybody for your inputs.

[Sagar Rohankar]

Ulf Dittmer wrote:Matcher.matches() checks whether the entire region is matched by the regexp, not whether the pattern matches anywhere in the region; Matcher.find() does that.

Hmm, I missed that .. Thanks Ulf.