Kotlin count char in string

Count Occurrences of a Character in a String in Kotlin

As a seasoned developer, you’re likely already familiar with Spring. But Kotlin can take your developer experience with Spring to the next level!

• Add new functionality to existing classes with Kotlin extension functions.
• Use Kotlin bean definition DSL.
• Better configure your application using lateinit.
• Use sequences and default argument values to write more expressive code.

By the end of this talk, you’ll have a deeper understanding of the advanced Kotlin techniques that are available to you as a Spring developer, and be able to use them effectively in your projects.

1. Introduction

The String is a basic data type in a programming language. Therefore, it’s important to know the basic operations and typical use cases for a String. In this tutorial, we’ll see various methods of counting occurrences of a specific character in a String.

2. Using count()

A String is a sequence of characters. Thanks to that, we can use the string extension function to count occurrences of a single character. The count() function returns the number of characters matching the given predicate:

val string = "hello world, baeldung" assertEquals(2, string.count < it == 'e' >)

3. Using Iteration

The easiest way to obtain occurrences of character is to iterate over the characters in the string using a for-loop. Then, we can increment the counter if the current character matches the specified character:

val string = "hello world, baeldung" var counter = 0 for (c in string) < if (c == 'e') < counter++ >> assertEquals(2, counter)

4. Using replace()

Another way to count occurrences is using the replace() extension function. Firstly, we can remove all occurrences of the specified character from the string using the replace() function. As a result, it returns a new string without the character we replaced. Further, we can calculate the difference between the new string length and that of the original string. The result will be the number of occurrences of the specified character. Let’s see an example:

val string = "hello world, baeldung" val count = string.length - string.replace("e", "").length assertEquals(2, count)

5. Using Regular Expressions

Another method to count occurrences is to use regular expressions. We can compile our character as a regular expression, and then, we create a matcher and count the matched occurrences:

val string = "hello world, baeldung" val matcher = Pattern.compile("e").matcher(string) var counter = 0 while (matcher.find()) < counter++ >assertEquals(2, counter)

6. Using the Map Collection

Let’s try to count occurrences using map collection. Firstly, we can store the count of each distinct character present in the string by iterating over it. The keys in the map are characters from the string, so we can easily access occurrences values by a specific character:

val string = "hello world, baeldung" val occurrencesMap = mutableMapOf() for (c in string) < occurrencesMap.putIfAbsent(c, 0) occurrencesMap[c] = occurrencesMap[c]!! + 1 >assertEquals(2, occurrencesMap['e'])

7. Conclusion

In this article, we’ve seen the most common ways to count specific character occurrences in a string in Kotlin. Kotlin provides some useful built-in functions that allow our code to be cleaner and follow the conventions of the language. We also saw some more complex solutions to this problem. As usual, all the examples are available over on GitHub.

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Count occurrences of a given character in a string in Kotlin

This article explores different ways to count occurrences of a given character in a string in Kotlin.

1. Using filter() function

The recommended solution is to use the filter() function to count occurrences of the given character in a string.

2. Using replace

Another solution is to remove all occurrences of the specified character from the string and return the difference of its length with that of the original string.

3. Using Regex

You can also use regular expressions to split the string based on pattern and count the matched occurrences.

4. Using Frequency Map

If the total number of lookups is more, consider creating a frequency map to do lookups in constant line efficiently. A frequency map stores count of each distinct character present in the string.

5. Custom Routine

Another plausible way is to write your routine for this simple task. The idea is to iterate over the characters in the string using a for-loop and increment the counter if the current character matches the specified character.

That’s all about counting occurrences of a given character in a string in Kotlin.

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Java Guides

In this blog post, we will learn how to write a Kotlin program to count the occurrence of a character in a String.

Counting the occurrence of a character in a string is a common programming task. It allows us to determine the frequency of a specific character within a given string. In this blog post, we will explore a Kotlin program that efficiently counts the occurrence of a character in a string. We will walk through the program step by step, explaining the logic behind it.

Kotlin Program: Counting the Occurrence of a Character in a String

To count the occurrence of a character in a string in Kotlin, we can follow a straightforward approach. Let’s dive into the code:

fun countOccurrences(str: String, ch: Char): Int < var count = 0 for (element in str) < if (element == ch) < count++ >> return count > fun main()

The character 'o' occurs 2 times in the string. The character 'l' occurs 3 times in the string.

The countOccurrences() function takes a string str and a character ch as input and returns the count of occurrences of ch in str.

We initialize a variable count to 0 to keep track of the occurrence count.

We iterate through each character element in the str string using a for loop.

Inside the loop, we compare each element with the given character ch. If they are equal, we increment the count by 1.

After iterating through all the characters in the string, we return the final count value.

In the main() function, we create a sample input string (val inputString = «Hello, World!») and specify the character we want to count (val character = ‘o’).

We call the countOccurrences() function with the input string and character, and the returned occurrence count is stored in the occurrenceCount variable.

Finally, we print the result to the console using println().

Conclusion

In this blog post, we have discussed a Kotlin program that efficiently counts the occurrence of a character in a given string. This program can be used to analyze text data, perform character frequency analysis, or identify patterns within strings.

Feel free to explore and modify the code to suit your specific needs. The concept of counting occurrences is essential in various programming scenarios, such as text processing, data analysis, and algorithmic challenges. Happy coding!

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