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.