java中继承与初始化顺序

该代码从Thinking in java第四版中拷贝，很好的反应了java中含有static成员与方法的继承初始化顺序，推荐阅读Thinking in java的原文。

代码如下：

class Insect {
    private int i = 9;
    protected int j;
    Insect(){
        System.out.println("i = " + i + ", j = " + j);
        j = 49;
    }
    private static int x1 = printInit("static Insect.x1 initialized");
    static int printInit(String s) {
        System.out.println(s);
        return 47;
    }
}

public class Beetle extends Insect{
    private int k = printInit("Beetle.k initialized");
    public Beetle() {
        System.out.println("k = " + k);
        System.out.println("j = " + j);
    }
     private static int x2 = printInit("static Beetle.x2 initialized");
     
     public static void main(String[] args) {
         System.out.println("Beetle constructor");
         Beetle b = new Beetle();
     }
}

得到的结果如下：

static Insect.x1 initialized
static Beetle.x2 initialized
Beetle constructor
i = 9, j = 0
Beetle.k initialized
k = 47
j = 49

可以看出，在main方法new出对象之前，先创建了基类的静态成员，然后创建了子类的静态成员，(这里静态成员的赋值用到了静态函数)，然后在main函数中new出对象的过程中，先调用了基类的构造方法，然后调用子类的构造方法。