Splitting lines regular expression in Java

Question

I want to parse an almost program. The program is consisted of two lines and it is shown below:

java.io.*;
java.lang.*;

I am using a library, which reads the whole program and splits it using the command

String[] words = sourceCode.split("[\\s+|\\W+]");

What it is produced by that is the following

words[0] = "Java"
words[1] = "io"
words[2] = ""
words[3] = ""
words[4] = ""
words[5] = ""
words[6] = Java
words[7] = "lang"
words[8] = ""
words[9] = ""
words[10] = ""
words[11] = ""

However, What I want is to break that program in lines first, and after that at a line's component. That is, I am using

String[] allLines = file1String.split("[\n]");
String[][] wordsOfALine =new String[allLines.length][];
for (int i=0;i<allLines.length;i++){
       wordsOfALine[i] = allLines[i].split("[\\s+|\\W+]").clone();
}

However, what I am getting here is

wordsOfALine[0][0] = "Java"
wordsOfALine[0][1] = "io"
wordsOfALine[1][0] = "Java"
wordsOfALine[1][1] = "lang"

And therefore all the empty words have now disappeared. Do you know how I can bring them back? I need to be consistent with the library...

Thanks

I think I'd use a lexer rather than a regex for this, but that may only reflect my own biases... — keshlam
– keshlam, Commented Mar 17, 2014 at 2:15

Bohemian · Accepted Answer · 2014-03-17 03:42:17Z

2

Firstly, your split regex is a giant bug. This expression:

"[\\s+|\\W+]"

means any single character that is one of:

whitespace
the plus sign +
the pipe char |
a non-word char (which includes whitespace btw)

It should be just:

"\\W"

Also if you add an extra parameter to the split call (see javadoc for why), you'll get trailing blank split terms.

This produces the output you want:

allLines[i].split("\\W", -1)

edited Mar 17, 2014 at 3:42

answered Mar 17, 2014 at 3:16

Bohemian♦

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myqyl4 · Accepted Answer · 2014-03-17 02:53:53Z

0

Try the following and modify as needed.

String[] allLines = file1String.split("[\n]");
String[] wordsOfALine = {};
int k = 0;
for (int i=0 ;i<allLines.length;i++){
   String[] words= allLines[i].split("[\\r\\n]+]");
   for(int j = 0; j < lines.length; j++){
      wordsOfALine[k++] : " + words[j]);
   }
}

answered Mar 17, 2014 at 2:53

myqyl4

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