Java: Split String around "+"

Question

Just found out, that I get a NullPointerException when trying to split a String around +, but if I split around - or anything else (and change the String as well of course), it works just fine.

String string = "Strg+Q";
String[] parts = string.split("+");
String part1 = parts[0]; //Strg
String part2 = parts[1]; //Q

Would love to hear from you guys, what I am doing wrong!

This one works:

String string = "Strg-Q";
String[] parts = string.split("-");
String part1 = parts[0]; //Strg
String part2 = parts[1]; //Q

**Why** does `+` make, specifically, a NPE? – ifly6 May 18 '18 at 20:11 — ifly6, May 18 '18 at 20:11

Amit Bera · Answer 1 · 2018-05-18T19:56:54.933

4

As + is one of the special regex syntaxes you need to escape it. Use

String[] parts = string.split("\\+");

Instead of

String[] parts = string.split("+");

edited May 18 '18 at 19:56

answered May 18 '18 at 19:52

Amit Bera

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Thanks for your help! silly mistake from me :-) – Bambi May 18 '18 at 19:55
@Bambi Happy to help you!!! – Amit Bera May 18 '18 at 19:57

score 3 · Answer 2 · answered May 18 '18 at 19:53

3

It happens because + is a special character in Regex - it's the match-one-or-more quantifier.

The only thing you need to do is to escape it:

String[] parts = string.split("\\+");

answered May 18 '18 at 19:53

Nikolas Charalambidis

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Thanks for your help! silly mistake from me :-) – Bambi May 18 '18 at 19:55

score 3 · Answer 3 · answered May 18 '18 at 19:54

3

String.split(...) expects a Regular Expression and the '+' is a special character. Try:

 String string = "Strg+Q";
 String[] parts = string.split("[+]");
 String part1 = parts[0]; //Strg
 String part2 = parts[1]; //Q

answered May 18 '18 at 19:54

Tobias Roloff

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score 3 · Accepted Answer · edited May 18 '18 at 20:13

3

Try this:

final String string = "Strg+Q";
final String[] parts = string.split("\\+");
System.out.println(parts[0]); // Strg
System.out.println(parts[1]); // Q

edited May 18 '18 at 20:13

Pshemo

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answered May 18 '18 at 19:55

Arun

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Downvoted because you've wrapped Java code in a Javascript code snippet. That's wrong – ifly6 May 18 '18 at 20:11

score 2 · Answer 5 · answered May 18 '18 at 19:53

2

+ is a special regex character which means that you need to escape it in order to use it as a normal character.

 String[] parts = string.split("\\+");

answered May 18 '18 at 19:53

Turamarth

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Thanks for your help! silly mistake from me :-) – Bambi May 18 '18 at 19:55

score 2 · Answer 6 · answered May 18 '18 at 19:54

2

The problem you got here is that "+" is a meta character in Java, so you need to "scape" it by using "\\+".

answered May 18 '18 at 19:54

A.Martinez

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score 2 · Answer 7 · answered May 18 '18 at 20:07

As others have mentioned, '+' is special when dealing with regex. In general, if a character is special you can use Pattern.quote() to escape it, as well as "\\+". Documentation on Pattern: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Example:

String string = "Strg-Q";
String[] parts = string.split(Pattern.quote("+"));
String part1 = parts[0]; //Strg
String part2 = parts[1]; //Qenter code here

Remember to import pattern from java.util.regex!

score 1 · Answer 8 · answered May 18 '18 at 19:55

Amit beat me too it. string.split() takes a regular expression as its argument. In regexes + is a special symbol. Escape it with a backslash. Then, since it's a java string, escape the backslash with another backslash, so you get \+. Try testing your regular expressions on an online regex tester.

Java: Split String around "+"

8 Answers8