java string.split() issue

Question

While solving a UVa question, I got this String and I need to split it an array of String removing # and @

Brazil#2@1#Scotland

I was getting a ArrayOutOfBounds exception when I used,

matchSummary.split("#@");

after researching solutions for this UVa question, I found that other experienced competitive programmers have done it like this,

string.split("[#@]");

and this passes the verdict of online judge.

I cant get this String split for this aforementioned String

My complete solution for this question is available here- see

Can anybody explain to me why my code worked with split("[#@]");?

"i need to split it an array of string removing # and @" — How should the final array look like? — Amal
– Amal, Commented Jul 29, 2014 at 20:15
You tagged this question as regex - any decent regex tutorial should quickly tell you the difference between "#@" and "[#@]". — Alex
– Alex, Commented Jul 29, 2014 at 20:17

Mena · Accepted Answer · 2014-07-29 20:22:49Z

2

In Java regular expressions, characters enclosed in square brackets [] are called a character class.

This...

String input = "Brazil#2@1#Scotland";
System.out.println(Arrays.toString(input.split("[#@]")));

... will split the String with either delimiter # or @, regardless of the order, and output:

[Brazil, 2, 1, Scotland]

It is equivalent in this case to:

System.out.println(Arrays.toString(input.split("#|@")));

However, splitting with #@ not enclosed by [] would search for a sequence of # followed by @.

This would not trigger any ArrayIndexOutOfBoundsException per se, it would just return a 1-sized array containing the original input String.

However, you're probably assuming the array size as > 1 later in the code, hence the Exception.

edited Jul 29, 2014 at 20:22

answered Jul 29, 2014 at 20:17

Mena

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gtgaxiola · Accepted Answer · 2014-07-29 20:16:26Z

2

Basically using: split("#@");

Will try to split only if it matches the characters # @ concurrently

by using:

split("[#@]");

You are selecting from the class to either split on # or @

answered Jul 29, 2014 at 20:16

gtgaxiola

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Vennik · Accepted Answer · 2014-07-29 20:15:56Z

1

[#@] means it will split on the # or the @.

For more information: http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

answered Jul 29, 2014 at 20:15

Vennik

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user2300851 · Accepted Answer · 2014-07-29 20:17:38Z

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The reason why the split function is giving you an error is because @ and # are not together in the string, i would suggest using the StringTokenizer to split the string.

so create a new instance of it - StringTokenizer s = new StringTokenizer("Brazil#2@1#Scotland");

then set the delimeter to @ then split them, and then split them with the delimeter #

answered Jul 29, 2014 at 20:17

user2300851

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