Regular Expression Example in KOTLIN - Check EMAIL address and more

 

Represents a compiled regular expression. Provides functions to match strings in text with a pattern, replace the found occurrences and split text around matches.

Here are some examples;

1. Check Email address valid or not (using matches )

println(".....email pattern check....")
val emails = listOf("abc_d@gmail.com", "test!@hotmail.com","abc_d@mailcom",
        "343434ffsdkfs#mail", "p6060606@gmail.com","_testmaail$@last.com")

val emailPattern = "[a-zA-Z0-9._-]+@[a-zA-Z0-9-]+\\.[a-zA-Z.]{2,18}".toRegex()

emails.forEach { email ->
    if (emailPattern.matches(email)) {
        println("$email matches")
    } else {
        println("$email does not match")
    }
}

output:

/* .....email pattern check....
 abc_d@gmail.com matches 
 test!@hotmail.com does not match
 abc_d@mailcom does not match
 343434ffsdkfs#mail does not match
 p6060606@gmail.com matches 
 _testmaail$@last.com does not match
 */

2.  Find the exact substring(partially word) inside the words in list

 - containsMatchIn

- matches

val testWords = listOf("test", "testified", "testing", "techtest",
        "exam","labtest", "roadtest", "protest", "tstom", "testimonials")

val pattern = "test".toRegex()

println("*********particular sub string inside the string************")
println("containsMatchIn function")

testWords.forEach{ word ->
    if(pattern.containsMatchIn(word)){
        println("$word matches")
    }else{
        println("$word  not matches")
    }
}



println("********* exact string to another string ************")
println("matches function")

testWords.forEach { word ->
    if (pattern.matches(word)) {
        println("$word matches")
    }else{
        println("$word not matches")
    }
}

output

/**********particular sub string inside the string************
containsMatchIn function
        test matches
        testified matches
        testing matches
        techtest matches
        exam  not matches
        labtest matches
        roadtest matches
        protest matches
        tstom  not matches
        testimonials matches
********* exact string to another string ************
matches function
        test matches
        testified not matches
        testing not matches
        techtest not matches
        exam not matches
        labtest not matches
        roadtest not matches
        protest not matches
        tstom not matches
        testimonials not matches */

3. Find only only from the string or sentence - findAll

findAll

println("....find only numbers.....")
val findNumInText = "Use numerals, however, when the number modifies a unit of measure, time, proportion, etc.: 2 inches, 5-minute delay, 65 mph, 23 years old, page 23, 2 percent. "

val patternN = "\\d+".toRegex()
val founds = patternN.findAll(findNumInText)

founds.forEach { num ->
    val foundValue = num.value
    println(foundValue)
}

output

/*....find only numbers.....
2
5
65
23
23
2*/

4. Find particular word and its indices in sentence 

println("...Find particular word and its indices in sentence...using\\\\b operator......")
val sent = "But you never know now do you now do you now do you."
val patternIs = "\\byou\\b".toRegex()
val matchesIS = patternIs.findAll(sent)
matchesIS.forEach { word ->
    val value = word.value
    val index = word.range
    println("$value found at indexes: $index")
}

output:

/* ...Find particular word and its indices in sentence...using\\b operator......
 you found at indexes: 4..6
 you found at indexes: 26..28
 you found at indexes: 37..39
 you found at indexes: 48..50
 */

If you want know more about regex, please check out this: 

https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.text/-regex/

https://docs.oracle.com/javase/8/docs/api/java/util/regex/Pattern.html