Java List to String array. 리스트를 스트링으로

Java List to String array

자바에서 List<String> 타입을 String array (String 배열)로 변환하는 방법은 다음과 같다

1. String.join 메소드

List<String> list = Arrays.asList("수", "영", "김");
String joined = String.join(" and ", list); 

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2. Collectios.joining 메소드

class Person {
  private String firstName;

  private String lastName; 


  public Person(String firstName, String lastName) {
    this.firstName = firstName;
    this.lastName = lastName;
  }

  public String getFirstName() {
    return this.firstName;
  }

  public String getLastName() {
    return this.lastName;
  }

}

// client code 

List<Person> list = Arrays.asList(
  new Person("영수", "김"),
  new Person("수영", "김"),
  new Person("별", "김")
);

String joinedFirstNames = list.stream()
  .map(Person::getFirstName)
  .collect(Collectors.joining(", "))

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3. Java.util.StringJoiner

• https://docs.oracle.com/javase/8/docs/api/java/util/StringJoiner.html

StringJoiner sj = new StringJoiner(":", "[", "]");
sj.add("George").add("Sally").add("Fred");

String desiredString = sj.toString();


List<Integer> numbers = Arrays.asList(1, 2, 3, 4);

String commaSeparatedNumbers = numbers.stream()
    .map(i -> i.toString())
    .collect(Collectors.joining(", "));

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4. apach commons

• org.apache.commons.lang.StringUtils.join(list, conjunction);

 

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5. Spring

• org.springframework.util.StringUtils.collectionToDelimitedString(list, conjunction);