Выдает ошибку: invalid method declaration; return type required. Вообще не понимаю где тут ошибка, помогите!

public class Main { int number; String name; int century; public Artifact (int number, String name, int century){ this.number = number; this.name = name; this.century = century; } public Artifact (int number, String name){ this.number = number; this.name = name; } public Artifact (int number){ this.number = number; } public static void main(String[] args) { Artifact artifact1 = new Artifact(123, "Maya", 11); Artifact artifact2 = new Artifact(1234, "Aztec"); Artifact artifact3 = new Artifact(12345); System.out.println(artifact1.number, artifact1.name, artifact1.century); System.out.println(artifact2.number, artifact2.name); System.out.println(artifact3.number); } }