How Can Regular Expressions Extract Numbers from a String and Store Them as an Integer Array?

Extracting Numbers from Strings Using Regular Expressions

Problem:

Given a string containing both text and numbers, how can we extract these numbers and store them in an array of integers?

Solution with Regular Expressions:

Regular expressions (regex) can be used as a concise and efficient method to match and extract specific patterns from strings. Here's how we can use regex to solve this problem:

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

String line = "There are more than -2 and less than 12 numbers here";

Pattern p = Pattern.compile("-?\d+");
Matcher m = p.matcher(line);

LinkedList<String> numbers = new LinkedList<>();
while (m.find()) {
  numbers.add(m.group());
}

// Convert the extracted strings to integers
int[] intArray = new int[numbers.size()];
for (int i = 0; i < numbers.size(); i++) {
  intArray[i] = Integer.parseInt(numbers.get(i));
}

System.out.println(intArray);

In this solution:

• We compile the regex pattern -?d , which matches numbers preceded by an optional negative sign (-).
• We use the Matcher object to find all occurrences of this pattern in the string.
• We store the matched numbers in a linked list of strings.
• Finally, we convert the extracted strings to integers and store them in an array of ints.

This approach provides a clean and reusable solution for extracting numbers from strings of arbitrary length and complexity.

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