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How to extract all numbers from a string in Kotlin

How to extract all numbers from a string in Kotlin.

Here's a detailed step-by-step tutorial on how to extract all numbers from a string in Kotlin:

Step 1: Create a Kotlin function to extract the numbers​

To start, create a Kotlin function that takes a string as input and returns a list of all the numbers found in the string. You can name the function "extractNumbers" or choose any other suitable name.

Step 2: Initialize an empty list to store the numbers​

Inside the function, initialize an empty mutable list that will be used to store the extracted numbers. You can use the MutableList interface to create the list.

fun extractNumbers(inputString: String): List<Int> {
    val numbers = mutableListOf<Int>()
    // Rest of the code goes here
    return numbers
}

Step 3: Use regular expressions to find numbers in the string​

Regular expressions are a powerful way to match patterns in strings. In Kotlin, you can use the built-in Regex class to work with regular expressions.

Inside the function, create a regular expression pattern that matches numbers. For example, you can use the pattern \d+ to match one or more digits.

fun extractNumbers(inputString: String): List<Int> {
    val numbers = mutableListOf<Int>()
    val pattern = Regex("\\d+")
    // Rest of the code goes here
    return numbers
}

Step 4: Find all matches of the pattern in the string​

To extract numbers from the input string, use the findAll() function of the Regex class. This function returns a Sequence of MatchResult objects, which represent the matches found in the string.

fun extractNumbers(inputString: String): List<Int> {
    val numbers = mutableListOf<Int>()
    val pattern = Regex("\\d+")

    pattern.findAll(inputString).forEach { matchResult ->
        // Rest of the code goes here
    }

    return numbers
}

Step 5: Convert the matched strings to numbers and add them to the list Inside the forEach loop, you can access each matched string using the value property of the MatchResult object. To convert the string to a number, you can use the toInt() function.

fun extractNumbers(inputString: String): List<Int> {
    val numbers = mutableListOf<Int>()
    val pattern = Regex("\\d+")

    pattern.findAll(inputString).forEach { matchResult ->
        val numberString = matchResult.value
        val number = numberString.toInt()
        numbers.add(number)
    }

    return numbers
}

Step 6: Test the function​

To test the function, call it with a sample input string and print the result. For example:

fun main() {
    val inputString = "I have 10 apples and 5 oranges"
    val numbers = extractNumbers(inputString)
    println(numbers)
}

This will output [10, 5], which are the numbers extracted from the input string.

And that's it! You now have a function that can extract all numbers from a string in Kotlin. You can customize the function further based on your specific requirements, such as handling decimal numbers or negative numbers.