Java: Parsing a string based on delimiter

Question

I have to design an interface where it fetches data from machine and then plots it. I have already designed the fetch part and it fetches a string of format A&[email protected]$13400$13400$13386$13418$13427$13406$13383$13406$13412$13419$00000$00000$

First five A&B@. characters are the identifier. Please note that the fifth character is new line feed i.e. ASCII 0xA.

The function I have written -

   public static boolean checkStart(String str,String startStr){

       String Initials = str.substring(0,5);
       System.out.println("Here is start: " + Initials);       
       if (startStr.equals(Initials))
        return true;
        else
        return false;
     }

shows Here is start: A&B@. which is correct.

Question 1: Why do we need to take str.substring(0,5) i.e. when I use str.substring(0,4) it shows only - Here is start: A&B@ i.e. missing new line feed. Why is New Line feed making this difference.

Further to extract remaing string I have to use s.substring(5,s.length()) instead of s.substring(6,s.length())

i.e. s.substring(6,s.length()) produces 3409$13400$13400$13386$13418$13427$13406$13383$13406$13412$13419$00000$00000$ i.e missing the first char after the identifier A&B@.

Question 2:

My parsing function is:

public static String[] StringParser(String str,String del){
    String[] sParsed = str.split(del);
     for (int i=0; i<sParsed.length; i++) {
                     System.out.println(sParsed[i]);
              }
    return sParsed;
     }

It parses correctly for String String s = "A&[email protected]/13400/13400/13386/13418/13427/13406/13383/13406/13412/13419/00000/00000/"; and calling the function as String[] tokens = StringParser(rightChannelString,"/");

But for String such as String s = "A&[email protected]$13400$13400$13386$13418$13427$13406$13383$13406$13412$13419$00000$00000$" , the call String[] tokens = StringParser(rightChannelString,"$"); does not parse the string at all.

I am not able to figure out why this behaviour. Can any one please let me know the solution?

Thanks

What is StringParser doing? Does it use regular expressions? — Henry
– Henry, Commented Oct 4, 2013 at 8:59
@Henry Please see StringParser definition. Edited to show its functionality — Gaurav K
– Gaurav K, Commented Oct 4, 2013 at 9:02
@what'up The problem I asked is different, my code works for one scenario but does not work for another. Instead of negative vote .. solution would have helped me better. I am not a java expert — Gaurav K
– Gaurav K, Commented Oct 4, 2013 at 9:04

Davz · Accepted Answer · 2013-10-04 09:08:44Z

1

Regarding question 1, the java API says that the substring method takes 2 parameters:

beginIndex the begin index, inclusive.
endIndex the end index, exclusive.

So in your example

String: A&[email protected]
Index:  01234567

substring(0,4) = indexes 0 to 3 so A&B@, that's why you have to put 5 as the second parameter to recover your line delimiter.

Regarding question 2, I guess that the split method takes a regexp in parameter and $ is a special character. To match the dollar sign I guess you have to escape it with the \ character (as \ is a special char in strings so you must also escape it).

String[] tokens = StringParser(rightChannelString,"\\$");

answered Oct 4, 2013 at 9:08

Davz

1,53012 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Henry · Accepted Answer · 2013-10-04 09:10:15Z

1

Q1: review the description of substring in the documentation:

Returns a new string that is a substring of this string.
The substring begins at the specified beginIndex and extends to the
character at index endIndex - 1. Thus the length of the substring
is endIndex-beginIndex.

Q2: the split method takes a regular expression for the separator. $ is a special character for regular expressions, it matches the end of the line.

answered Oct 4, 2013 at 9:10

Henry

43.9k7 gold badges75 silver badges89 bronze badges

Collectives™ on Stack Overflow

Java: Parsing a string based on delimiter

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related