private 생성자에 관한 예제입니다.

Singleton.java

/**
 * Created by mindwing on 2015-12-12.
 */
public class Singleton {
    private static Singleton instance = new Singleton();

    private Singleton() {
    }

    public static Singleton getInstance() {
        return instance;
    }
}

SingletonTest.java

/**
 * Created by mindwing on 2015-12-12.
 */
public class SingletonTest {
    public static void main(String[] args) {
        // Singleton 클래스의 생성자가 private !!!
        // Singleton singleton = new Singleton();

        Singleton singleton = Singleton.getInstance();
    }
}