[22] 코딩해보세요. static 과 singleton pattern(유일한 객체)

package cardex;

public class Card {	

	private int cardNumber;
	private static int serialNumber = 10000;
	
	
     Card() { // 카드가 생성될때마다 수가 증가
		serialNumber++;
		cardNumber = serialNumber;	
	}
	
	public int getCardNumber() {
		return cardNumber;
	}
	
	public void setCardNumber(int cardNumber) {
		this.cardNumber = cardNumber;
	}
}

 

package cardex;

public class CardCompany {

	private static CardCompany instance = new CardCompany(); // 싱글톤 패턴 
	

	private CardCompany() {}
	
	
	public static CardCompany getInstance() { // 리턴 클래스 
		if(instance == null) {
			instance = new CardCompany();
		} 
		return instance;
	}
	
	public Card createCard() { // 리턴값은 Card 클래스  ( 메소드에서 Card 생성 ) 
		Card card = new Card();
			return card;
	}
}