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Merge pull request #879 from yadavan88/extract-numbers
Extracting number from string
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‎core-kotlin-modules/core-kotlin-strings-5/README.md

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## Core Kotlin Strings
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This module contains articles about core Kotlin strings.
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### Relevant Articles
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‎core-kotlin-modules/core-kotlin-strings-5/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<artifactId>core-kotlin-strings-5</artifactId>
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<name>core-kotlin-strings-5</name>
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<packaging>jar</packaging>
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<parent>
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<groupId>com.baeldung</groupId>
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<artifactId>core-kotlin-modules</artifactId>
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<version>1.0.0-SNAPSHOT</version>
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</parent>
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<dependencies>
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<dependency>
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<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-params</artifactId>
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<version>5.10.2</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎core-kotlin-modules/core-kotlin-strings-5/src/test/kotlin/com/baeldung/extractnumber/NumberExtractUnitTest.kt

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package com.baeldung.extractnumber
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import org.junit.jupiter.api.Assertions
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import org.junit.jupiter.api.Test
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import org.junit.jupiter.params.ParameterizedTest
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import org.junit.jupiter.params.provider.CsvSource
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import java.math.BigInteger
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fun extractUsingRegex(str: String): BigInteger? {
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return Regex("\\d+").find(str)?.value?.toBigIntegerOrNull()
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}
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fun extractMultipleUsingRegex(str: String): List<BigInteger> {
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return Regex("\\d+").findAll(str).map { it.value.toBigInteger() }.toList()
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}
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fun extractNumbersUsingSplitAndRegex(str: String): List<BigInteger> {
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return str.split(Regex("\\D+"))
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.filter { it.isNotBlank() }
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.map { it.toBigInteger() }
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}
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fun extractNumbersUsingLoop(str: String): List<BigInteger> {
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val numbers = mutableListOf<BigInteger>()
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val currentNumber = StringBuilder()
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for (char in str) {
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if (char.isDigit()) {
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currentNumber.append(char)
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} else if (currentNumber.isNotEmpty()) {
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numbers.add(currentNumber.toString().toBigInteger())
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currentNumber.clear()
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}
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}
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if (currentNumber.isNotEmpty()) {
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numbers.add(currentNumber.toString().toBigInteger())
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}
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return numbers
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}
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class NumberExtractUnitTest {
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@ParameterizedTest
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@CsvSource(
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"string with 123 and 333 in the text, 123",
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"another string with 456 and 789, 456",
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"string 123-234, 123",
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"no numbers,",
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"3 4 50 numbers6, 3",
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"123456789large numbers0, 123456789",
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"91234567891011121314151617181920number,91234567891011121314151617181920"
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)
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fun `extract first occurrence of number from string using regex`(str: String, expected: String?) {
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val number = extractUsingRegex(str)
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Assertions.assertEquals(number, expected?.toBigIntegerOrNull())
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}
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@ParameterizedTest
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@CsvSource(
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"string with 123 and 333 in the text, 123:333",
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"another string with 456 and 789, 456:789",
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"string 123-234, 123:234",
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"no numbers,",
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"3 4 50 numbers6, 3:4:50:6",
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"123456789large numbers0, 123456789:0",
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"91234567891011121314151617181920number,91234567891011121314151617181920"
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)
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fun `extract all occurrences of numbers from string using regex`(str: String, expected: String?) {
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val numbers = extractMultipleUsingRegex(str)
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val expectedList = expected?.split(":")?.map { it.toBigInteger() } ?: emptyList()
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Assertions.assertEquals(expectedList, numbers)
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}
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@ParameterizedTest
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@CsvSource(
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"string with 123 and 333 in the text, 123:333",
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"another string with 456 and 789, 456:789",
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"string 123-234, 123:234",
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"no numbers,",
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"3 4 50 numbers6, 3:4:50:6",
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"123456789large numbers0, 123456789:0",
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"91234567891011121314151617181920number,91234567891011121314151617181920"
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)
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fun `extract all occurrences of numbers from string using split and regex`(str: String, expected: String?) {
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val numbers = extractNumbersUsingSplitAndRegex(str)
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val expectedList = expected?.split(":")?.map { it.toBigInteger() } ?: emptyList()
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Assertions.assertEquals(expectedList, numbers)
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}
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@ParameterizedTest
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@CsvSource(
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"string with 123 and 333 in the text, 123:333",
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"another string with 456 and 789, 456:789",
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"string 123-234, 123:234",
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"no numbers,",
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"3 4 50 numbers6, 3:4:50:6",
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"123456789large numbers0, 123456789:0",
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"91234567891011121314151617181920number,91234567891011121314151617181920"
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)
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fun `extract all occurrences of numbers from string using loop`(str: String, expected: String?) {
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val numbers = extractNumbersUsingLoop(str)
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val expectedList = expected?.split(":")?.map { it.toBigInteger() } ?: emptyList()
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Assertions.assertEquals(expectedList, numbers)
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}
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@Test
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fun `check empty string scenario for loop`() {
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val numbers = extractNumbersUsingLoop("")
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Assertions.assertIterableEquals(numbers, listOf<BigInteger>())
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}
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@Test
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fun `check empty string scenario for split`() {
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val numbers = extractNumbersUsingSplitAndRegex("")
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Assertions.assertIterableEquals(numbers, listOf<BigInteger>())
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}
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@Test
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fun `check empty string scenario for regex`() {
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val numbers = extractMultipleUsingRegex("")
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Assertions.assertIterableEquals(numbers, listOf<BigInteger>())
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}
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}

‎core-kotlin-modules/pom.xml

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<module>core-kotlin-strings-2</module>
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<module>core-kotlin-strings-3</module>
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<module>core-kotlin-strings-4</module>
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<module>core-kotlin-strings-5</module>
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<module>core-kotlin-string-conversions</module>
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<module>core-kotlin-files</module>
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<module>core-kotlin-operators</module>

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