Java: 基类、子类、构造函数、程序块的初始化顺序

初始化顺序

1. 基类static block
2. 子类static block
3. 基类non-static block
4. 子类non-static block
5. 基类constructor
6. 子类constructor

示例代码

public class Main {
    public static void main(String[] args) throws Exception {
        new Train();

        System.out.println("FINISH!");
    }
}

class Traffic {
    public Traffic() {
        System.out.println("Traffic constructor");
    }
    {
        System.out.println("Traffic non-static block");
    }
    static {
        System.out.println("Traffic static block");
    }
}

class Train extends Traffic {
    public Train() {
        System.out.println("Train constructor");
    }
    static {
        System.out.println("Train static block");
    }
    {
        System.out.println("Train non-static block");
    }
}

Traffic static block
Train static block
Traffic non-static block
Traffic constructor
Train non-static block
Train constructor
FINISH!

 

static成员的forward reference限制

• 记住这句话：Forward reference is not allowed on the right side of an assignment.