A Java 8 adaptation of code to find the first non-repeated letter in a string. Original found here: http://javahungry.blogspot.com/2013/12/first-non-repeated-character-in-string-java-program-code-example.html#.UsFH_N8Q8ak

Java8NonRepeatingString.java

import java.util.*;
import java.util.function.*;
import java.util.stream.Collectors;
import static java.util.function.Function.identity;

public class NonRepeatingLetter {
  
  public static void main(String[] args) {
    findFirstNonRepeatingLetter(args[0], System.out::println);
  }
  
  private static void findFirstNonRepeatingLetter(String s, Consumer<Character> callback) {
    s.chars()
      .mapToObj(i -> Character.valueOf((char) i))
      .collect(Collectors.groupingBy(identity(), LinkedHashMap::new, Collectors.counting()))
      .entrySet().stream()
      .filter(entry -> entry.getValue() == 1L)
      .map(entry -> entry.getKey())
      .findFirst().map(c -> { callback.accept(c); return c; } );
  }
}

Nice, just doing a bit of research and came across this. Lovely use of Java 8

Could you provide comments for those new to Java 8

could you please provide comments

What is use of identity function?