Taewon's road not taken

- stream, filter, predicate 사용 예제

import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

public class Playground {
    
    public static List<String> friends = Arrays.asList("taewon", "brian", "timmy", "turner", "ed", "edd", "eddy", "samuel", "jackson", "miranda", "Samantha", "sarah");
    
    public static void main(String[] args) {
        List<String> startsWithT = friends.stream()
                .filter(checkIfStartsWith("t"))
                .collect(Collectors.toList());

        List<String> startsWithE = friends.stream()
                .filter(checkIfStartsWith("e"))
                .collect(Collectors.toList());
    }
    
    public static Predicate<String> checkIfStartsWith(String letter) {
        return name -> name.startsWith(letter);
    }
}

- 총 길이 찾기 

import java.util.Arrays;
import java.util.List;

public class Playground {
    
    public static List<String> friends = Arrays.asList("taewon", "brian", "timmy", "turner", "ed", "edd", "eddy", "samuel", "jackson", "miranda", "Samantha", "sarah");
    
    public static void main(String[] args) {
        int sum = friends.stream()
                .mapToInt(name -> name.length())
                .sum();
    }
    
}

- 긴 이름 기준 조건으로 이름 찾기, optional 

import java.util.Arrays;
import java.util.List;
import java.util.Optional;

public class Playground {
    
    public static List<String> friends = Arrays.asList("taewon", "brian", "timmy", "turner", "ed", "edd", "eddy", "samuel", "jackson", "miranda", "Samantha", "sarah");
    
    public static void main(String[] args) {
        Optional<String> longestName = friends.stream()
                .reduce((name1, name2) -> name1.length() >= name2.length() ? name1 : name2);
        
        longestName.ifPresent(System.out::println);
    }
    
}

출처 : 

https://tomining.tistory.com/48