package reusing;

class A {
    public A(int a) {
        System.out.println("A()");
    }
}

class B {
    public B(int a) {
        System.out.println("B()");
    }
}

class C extends A {
    public C() {
        super(10);
        System.out.println("C()");
    }

    B b = new B(10);
}

public class E05_SimpleInheritance {
    public static void main(String args[]) {
        new C();
    }
} /* Output: 
    A()
    B()
    C()
  */// :~

public class Demo1 {
    public static void main(String[] args) {
        B8 b1 = new B8();
        
    }
}


class A8{
    public A8(int a){
        System.out.println("A8 constructor");
    }
}

class B8 extends A8{
    public B8() {
        super(10);　　//，由于A8没有默认构造器，如果这行注释了，编译器会报错
        System.out.println("B81");
    }
}

　　你必须在构造器的第一行放置super或者this构造器，否则编译器会自动地放一个空参数的super构造器的，其他的构造器也可以调用super或者this，调用成一个递归构造链，最后的结果是父类的构造器（可能有多级父类构造器）始终在子类的构造器之前执行，递归的调用父类构造器。

public class Object {
...
public Object() {}
...
}

public class Employee extends Object {
    private String name;
    private double salary = 15000.00;
    private Date birthDate;
    public Employee(String n, Date DoB) {
        // implicit super();
        name = n;
        birthDate = DoB;
    }
    public Employee(String n) {
        this(n, null);
    }
}

public class Manager extends Employee {
    private String department;
    public Manager(String n, String d) {
        super(n);
        department = d;
    }
}