相关疑难解决方法(0)

究竟什么是默认构造函数 - 你能告诉我以下哪一个是默认构造函数,以及它与其他构造函数的区别是什么？

public Module() {
   this.name = "";
   this.credits = 0;
   this.hours = 0;
}

public Module(String name, int credits, int hours) {
   this.name = name;
   this.credits = credits;
   this.hours = hours;
}

请考虑以下代码

  class Meal {
    Meal() { System.out.println("Meal()"); }
  }

  class Bread {
    Bread() { System.out.println("Bread()"); }
  }

  class Cheese {
    Cheese() { System.out.println("Cheese()"); }
  }

  class Lettuce {
    Lettuce() { System.out.println("Lettuce()"); }
  }

  class Lunch extends Meal {
    Lunch() { System.out.println("Lunch()"); }
  }

  class PortableLunch extends Lunch {
    PortableLunch() { System.out.println("PortableLunch()");}
  }

  class Sandwich extends PortableLunch {
    private Bread b = new Bread();
    private Cheese c = new Cheese();
    private Lettuce l = new Lettuce();
    public Sandwich() {
      System.out.println("Sandwich()");
    } …