In this tutorial, we will learn “Find the first non-repeating character in a string using Java 8?”. In order to do that, we are going to leverage the Stream API along with the Collectors.groupingBy collector.
Find the first non-repeated character in a string using Java 8
Find the first non-repeating character in a string using Java 8 Click To Tweet
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | /** * Using Java 8, Find the first non-repeating character in a string * @author Deepak Verma * */ import java.util.LinkedHashMap; import java.util.Map; import java.util.Optional; import java.util.function.Function; import java.util.stream.Collectors; public class Find_first_non_repeating_character_in_string_Java8Stream { public static void main(String[] args) { String inputString = "Techndeck"; Optional<Character> ourcome = findFirstNonRepeatedCharacter(inputString); ourcome.ifPresentOrElse( character -> System.out.println("First Non-Repeated Character: " + character), () -> System.out.println("There is No non-repeated character present in the string.") ); } public static Optional<Character> findFirstNonRepeatedCharacter(String inputStr) { Map<Character, Long> charCountingMap = inputStr.chars() .mapToObj(c -> (char) c) .collect( Collectors.groupingBy( Function.identity(), LinkedHashMap::new, Collectors.counting() ) ); return charCountingMap.entrySet().stream() .filter(entry -> entry.getValue() == 1) .map(Map.Entry::getKey) .findFirst(); } } |
Output:
1 | First Non-Repeated Character: T |
check if text or string present in a file using java 8
The code above defines a method findFirstNonRepeatedCharacter that takes a string as input and returns an Optional<Character> which represents the first non-repeated character.
Steps:
- Convert the input string to a stream of characters using
chars(). - Convert each character to a
Characterobject. - Use
Collectors.groupingByto group the characters by their counts in aLinkedHashMap. - Filter the entries to find characters with a count of 1.
- Map the entry set to characters.
- Use
findFirstto get the first non-repeated character.
skip method java 8 stream
Find the first non-repeating character in a string using Java 8 Click To Tweet
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