Determine whether the regex pattern is positioned at the start of the string or following a designated character

Question

Determine whether the regex pattern is positioned at the start of the string or following a designated character

I am working with a regex pattern and need to verify if it matches at the start of a string, after a new line, or after a white space.

Additionally, I want to ensure that the pattern also matches the end of the string, after a new line, or a white space.

How can I create this "beginning or white space" condition without repeating myself?

For example:

"Crazy Fredrick bought many very exquisite opal jewels"

If searching for s, it should only match the last character "s" in "jewels". The "s" in "exquisite" should not be considered a match.

javascript regex match

Answer 1

Answer №1

If you are looking for words that start with T and end with s using regular expressions, you can simply split the sentence by space and then apply your custom regular expression pattern to each word individually.

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

public class CustomRegex {
   public static void main(String[] args) {
      Pattern pattern = Pattern.compile("^(T).*[s]$");
      Matcher matcher = pattern.matcher("This is a tests string");
      System.out.println(matcher.matches());
   }
}

Answer 2

If you are looking for words that start with T and end with s using regular expressions, you can simply split the sentence by space and then apply your custom regular expression pattern to each word individually.

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

public class CustomRegex {
   public static void main(String[] args) {
      Pattern pattern = Pattern.compile("^(T).*[s]$");
      Matcher matcher = pattern.matcher("This is a tests string");
      System.out.println(matcher.matches());
   }
}

Answer 3

Answer №2

When working with JavaScript, the \b character comes in handy. According to information on MDN's RegExp page, it is used to match a zero-width word boundary, like that between a letter and a space.

This means it can be helpful for pinpointing specific parts of words, such as in the case of "jewels".

To target the 's' at the end of the word "jewels", you could implement the following regex:

var regex = /s\b/g;

If you wish to locate every word ending with a "y", the regex pattern would look like this:

var regex = /\w*y\b/gi;

The outcome will be "Crazy, very, many", capturing all relevant words containing 'y' at the end.

Answer 4

When working with JavaScript, the \b character comes in handy. According to information on MDN's RegExp page, it is used to match a zero-width word boundary, like that between a letter and a space.

This means it can be helpful for pinpointing specific parts of words, such as in the case of "jewels".

To target the 's' at the end of the word "jewels", you could implement the following regex:

var regex = /s\b/g;

If you wish to locate every word ending with a "y", the regex pattern would look like this:

var regex = /\w*y\b/gi;

The outcome will be "Crazy, very, many", capturing all relevant words containing 'y' at the end.

Determine whether the regex pattern is positioned at the start of the string or following a designated character

Answer №1

Answer №2

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