collect() 스트림을 컬렉션과 배열로 전환하다: toList() toSet() toMap toCollection() toArray()

앞서 collect()의 기본 문법에 대해 알아봤다.

toList()를 사용하여 최종연산을 확인해봤는데 외 전환방법을 확인해보자.

https://standout.tistory.com/1463

collect(), 매개변수로 스트림을 최종연산하다: Object collect(Collector collector) Object collect(Supplier supplier

 

 

toList()
스트림의 요소를 리스트로 변환.

import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("Apple", "Banana", "Orange");
        List<String> list = stream.collect(Collectors.toList());
        System.out.println(list); // 출력: [Apple, Banana, Orange]
    }
}

 

 

 

toSet()
스트림의 요소를 집합으로 변환.

import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("Apple", "Banana", "Orange", "Apple");
        Set<String> set = stream.collect(Collectors.toSet());
        System.out.println(set); // 출력: [Apple, Orange, Banana]
    }
}

 

 

 

 

toMap()
스트림의 요소를 맵으로 변환.

import java.util.Map;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("Apple", "Banana", "Orange");
        Map<String, Integer> map = stream.collect(Collectors.toMap(s -> s, String::length));
        System.out.println(map); // 출력: {Apple=5, Banana=6, Orange=6}
    }
}

 

 

 

 

toCollection()
스트림의 요소를 특정 컬렉션으로 변환.

import java.util.ArrayList;
import java.util.stream.Collectors;
import java.util.stream.Stream;

public class Main {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("Apple", "Banana", "Orange");
        ArrayList<String> collection = stream.collect(Collectors.toCollection(ArrayList::new));
        System.out.println(collection); // 출력: [Apple, Banana, Orange]
    }
}

 

 

 

 

toArray()
스트림의 요소를 배열로 변환.

import java.util.stream.Stream;
import java.util.Arrays;

public class Main {
    public static void main(String[] args) {
        Stream<String> stream = Stream.of("Apple", "Banana", "Orange");
        String[] array = stream.toArray(String[]::new);
        System.out.println(Arrays.toString(array)); // 출력: [Apple, Banana, Orange]
    }
}