Java: How to extract substring between two characters from a string?

Question

I am relatively new to Java and I need some help to extract multiple substrings from a string. An example of a string is as given below:

String = "How/WRB can/MD I/PRP find/VB a/DT list/NN of/IN celebrities/NNS '/POS real/JJ names/NNS ?/."

Desired result: WRB MD PRP VB DT NN IN NNS POS JJ NNS

I have a text file with possibly thousands of similar POS-tagged lines that I need to extract the POS tags from and do some calculation based on the POS tags.

I have tried using tokenizer but didn't really get the result I wanted. I even tried using split() and saving to arrays because I need to store it and use it later and that still didn't work.

Lastly, I tried using Pattern Matcher and I am having problems with the regex as it return the word with the forward slash.

Regex: [\/](.*?)\s\b
Result: /WRB /MD ....

If there's a better way to do this, please let me know or if anyone can help me figure out what's wrong with my regex.

Answer 1

This should work:

String string = "How/WRB can/MD I/PRP find/VB a/DT list/NN of/IN celebrities/NNS '/POS real/JJ names/NNS ?/.";
System.out.println(string.replaceAll("[^/]+/([^ ]+ ?)", "$1"));

Prints: WRB MD PRP VB DT NN IN NNS POS JJ NNS .

Answer 2

If you still wanted to use pattern matching, look at positive lookbehinds. It will allow you to match a word that begins with a slash, but not actually match the slash itself.

An example would be something like this:

(?<=/).+?(?= |$)

Matches anything that starts with a slash, and is followed by a space OR the end of the string

Here is a working example written in Java:

import java.util.regex.Pattern;
import java.util.regex.Matcher;
import java.util.LinkedList;

public class SO {
    public static void main(String[] args) {
        String string = "How/WRB can/MD I/PRP find/VB a/DT list/NN of/IN celebrities/NNS '/POS real/JJ names/NNS ?/.";
        Pattern pattern = Pattern.compile("(?<=/).+?(?= |$)");
        Matcher matcher = pattern.matcher(string);

        LinkedList<String> list = new LinkedList<String>();

        // Loop through and find all matches and store them into the List
        while(matcher.find()) { 
            list.add(matcher.group()); 
        }

        // Print out the contents of this List
        for(String match : list) { 
            System.out.println(match); 
        }
    }
}

Answer 3

String string = "How/WRB can/MD I/PRP find/VB a/DT list/NN of/IN celebrities/NNS '/POS real/JJ names/NNS ?/.";

string = string .replaceAll("\\S+/", "").replace(".", "");  

System.out.println(string );