一个构造方法如果被私有化了，那么只能从该私有化类的内部进行实例化进行调用

class Con1{

    private static Con1 ins = new Con1();    //内部实例化构造方法；

    public static Con1 getIns(){ //通过静态方法获取实例化对象

        return ins;

    }

    private Con1(){ //私有化构造方法

    }

    public void print(){

        System.out.print("成功实例化");

    }

}

public class ConstructDemo {

    public static void main(String args[]){

        Con1 con1= null;

        con1 = Con1.getIns(); //取得实例化对象

        con1.print();

    }

私有化构造方法是一种单态设计方法，可以实现避免多次实例化；如：

public class ConstructDemo {

public static void main(String args[]){

Con1 con1= con1 = Con1.getIns();

Con1 con2= con1 = Con1.getIns();

Con1 con3= con1 = Con1.getIns();

Con1 con4= con1 = Con1.getIns();

Con1 con5= con1 = Con1.getIns();

con1.print();

con2.print();

con3.print();

con4.print();

con5.print();

   }

}

该功能的实现实际上只实例化了一次而已：private static Con1 ins = new Con1();    //内部实例化构造方法；