Split strings keeping all trailing empty elements

Question

I am relatively new to java programming. How would you split following lines of Strings separated by semicolons?

String; String; String; String, String; String;;String;
String; String; String; ;String;String;String;String

I would like to pass each String as an argument into a constructor (from txt file), but I am unable to find passable regex for the purpose. The constructor has 8 String arguments (from where there is nothing between two semicolons ;;, I would like to get an empty String). In this case two separate objects would be created. I am aware of how splitting a String generally works but this one seems to be too tricky for me.

Use the split method of String with the semicolon as separator — Stultuske
– Stultuske, Commented Dec 2, 2015 at 10:39
Why does it seem tricky? What are you trying to achieve and where are you stuck? Also, you have a comma in the first line (String, String) — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 2, 2015 at 10:40
Well. I tried (";"), ("\\W") and (\\;) regular expressions but I always get java.lang.ArrayIndexOutOfBoundsException. — Laarup
– Laarup, Commented Dec 2, 2015 at 10:48
@stribizhev Pls read the question again "The constructor has 8 String arguments (from where there is nothing between two semicolons ;;, I would like to get an empty String)" Your code doesn't return the last argument in the first case the OP has provided, tokens.length == 7 for that case — Ferrybig
– Ferrybig, Commented Dec 2, 2015 at 11:14
@ferrybig: That is not mine, that is Anordil's answer. Yes, the last empty element is omitted. I posted my answer where I am describing how to avoid omitting trailing empty elements. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Dec 2, 2015 at 11:44

Wiktor Stribiżew · Accepted Answer · 2015-12-02 11:40:11Z

6

The issue is the String.Split does not keep the trailing empty elements:

Trailing empty strings are therefore not included in the resulting array.

To include them, use -1 as the second argument (see demo):

String s  = "String; String; String; String, String; String;;String;";
System.out.println(Arrays.toString(s.split(";", -1)));

See this Java reference:

public String[] split(String regex, int limit)
The limit parameter controls the number of times the pattern is applied and therefore affects the length of the resulting array... If n is non-positive then the pattern will be applied as many times as possible and the array can have any length. If n is zero then the pattern will be applied as many times as possible, the array can have any length, and trailing empty strings will be discarded.

answered Dec 2, 2015 at 11:40

Wiktor Stribiżew

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Anordil · Accepted Answer · 2015-12-02 10:44:59Z

3

Your answer is in the javadoc.

String toto = "A;B;C;D";

String[] tokens = toto.split(";");

answered Dec 2, 2015 at 10:44

Anordil

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5 Comments

Murat Karagöz Over a year ago

There are double ; and a random ,. This is not going to work.

Anordil Over a year ago

Using split without any argument is the same as calling it with a limit of '0' tokens, which, according to the Javadoc, will indeed return empty matches.

Murat Karagöz Over a year ago

There is still the random ,.

Anordil Over a year ago

Which isn't a separator according to what the OP said, so it may very well be valid for an argument to contain a comma.

Laarup Over a year ago

Yes, that argument contains a comma.

Ferrybig · Accepted Answer · 2016-01-18 18:28:43Z

1

Since you stated that you want to contain the spaces, only split on the ; and want to keep 8 arguments for your constructor, we are going to use the split with a limit method.

String.split(String,int)

Example:

String in = "String; String; String; String, String; String;;String;";
String[] s1 = in.split(";");

Gives:

["String"," String"," String, String"," String"," String","","String"]

What is only 7 in length and will fail your constructor.

String[] s = in.split(";",8);

Gives:

["String"," String"," String"," String, String"," String","","String",""]`

What is 8 in length and will work.

You can then address your constructor using:

YourObject obj = new YourObject(s[0],s[1],s[2],s[3],s[4],s[5],s[6],s[7]);

edited Jan 18, 2016 at 18:28

answered Dec 2, 2015 at 11:13

Ferrybig

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