Java knowledge accumulation-static code blocks, non-static code blocks, execution sequence and times of Constructors

See the following program:

 1 class A { 2    static{ 3       System.out.println("A static"); 4    }    5  6    { 7       System.out.println("A not static");  8    }    9 10    public A(){11       System.out.println("A new");12    }13 }14 15 class B extends A{16    static{17       System.out.println("B static");18    }   19 20    {21       System.out.println("B not static"); 22    }  23 24    public B(){25       System.out.println("B new");26    }27 } 28 29 public class MainTest {30    public static void main(String[] args) {31       A ab= new B();32       ab= new B();33    }34 }

The output is as follows:

A static

B static

A Not static

A new

B Not static

B New

A Not static

A new

B Not static

B New

 

Conclusion: 

A static code block is called only once when the class is loaded into the memory for the first time.

Non-static code block. Each time an object is created, it is called before the constructor.

Constructor, called at the end of each object creation.

Create a parent class object before creating a subclass object.