シングルトーン(SingleTon)

SingleTonクラスの構成方法

例

モノトーンテスト

public class MySingleton {
	private static MySingleton single;
	
	private MySingleton() {
		// cf. enum도 접근제어자가 private이었음..
	}
	
	public static MySingleton getInstance() {
		if (single==null) {
			single = new MySingleton();
		}
		return single;
	}
	
	// 나머지  내용들은 이 클래스로 처리할 내용들을 기술한다.
	public void displayText() {
		System.out.println("난 싱글톤패턴의 객체!");
	}
}

public class SingletonTest {
	
	public static void main(String[] args) {
		// MySingleton test1 = new MySingleton(); //new명령 사용 불가
	
		// getInstance() 이용하여 객체 생성
		MySingleton test2 = MySingleton.getInstance();
		test2.displayText();
		MySingleton test3 = MySingleton.getInstance();
		
		System.out.println("test2 = "+test2);
		System.out.println("test3 = "+test3);
		
	}

}

メンバーをモノトーンとして使用

public class MemberDaoImpl implements IMemberDAO{
	
	private static IMemberDAO memDAO;
	
	private Connection conn;
	private Statement stmt;
	private PreparedStatement pstmt;
	private ResultSet rs;
	
	//외부에서 new 못함
	private MemberDaoImpl() {
		// TODO
	}

	public static IMemberDAO getInstance() {
		if(memDAO == null) {
			memDAO = new MemberDaoImpl();
		}
		return memDAO;
	}

public class MemberServiceImpl implements IMemberService{

	private static IMemberService memService;
	private IMemberDAO memDAO;
	
	private MemberServiceImpl() {
		memDAO = MemberDaoImpl.getInstance();
	}
	
	public static IMemberService getInstance() {
		if(memService == null) {
			memService = new MemberServiceImpl();
		}
		
		return memService;
}

public class MemberInfoMain {
	
	private IMemberService memService;
	private Scanner scan = new Scanner(System.in); 
	
	public MemberInfoMain() {
		memService = MemberServiceImpl.getInstance();
	}