Java基础知识回顾第三篇 - 语句块 | 构造方法 调用顺序问题

1、Java类中静态语句块、构造语句块以及构造函数的执行顺序

public class Test {

public Test() {

    System.out.println("A");

}

static{

    System.out.println("C");

}

{

    System.out.println("B");

}

public static void main(String[] args) {

    new Test();

}

}

该程序输出的结果为：CBA

由此可见他们三者的执行顺序如下：静态语句块 -> 构造语句块 -> 构造函数

2、父类和之类构造方法的调用顺序问题

class People {
    String name;

    public People() {
        System.out.print(1);
    }

    public People(String name) {
        System.out.print(2);
        this.name = name;
    }
}

class Child extends People {
    People father;

    public Child(String name) {
        System.out.print(3);
        this.name = name;
        father = new People(name + ":F");
    }

    public Child() {
        System.out.print(4);
    }
    
}

new Child("William");输出结果为：132
由此可见：默认调用父类无参的构造函数