scannerTest.java

public class ManualBallsGenerator {

    Scanner scanner;

    public ManualBallsGenerator() {
        this.scanner = new Scanner(System.in);
    }

    public BaseBalls generate() {
        System.out.println("숫자 3개 입력");
        return new BaseBalls(
            new ArrayList<>(Arrays.asList(scanner.nextInt(), scanner.nextInt(), scanner.nextInt()))
        );
    }

}