Java Common pen Questions < two >

1. Output order of static code block, non-static code block, constructor function

Case one: When the parent class is not inherited

1 classHelloa {2     3      PublicHelloa () {4System.out.println ("I ' M A class");5     }6 7     Static {8System.out.println ("Static A");9     }Ten      One     { ASystem.out.println ("A"); -     } -  the      Public Static voidMain (string[] args) { -         NewHelloa (); -         NewHelloa (); -     } +}

Output Result:

Static A
A
I ' M A class
A
I ' M A class

Analysis: The output order is: Static code block > Non-static code block > constructor, and no matter how many times the class static code block is executed only once, so the general situation of memory-intensive connection or other in the static code block, access speed, and only access once, save consumption.

Case two: When inheriting from a parent class

classHelloaextendshellob{ PublicHelloa () {System.out.println ("I ' M A class"); }    Static{System.out.println ("Static A"); } {System.out.println (A); }     Public Static voidMain (string[] args) {NewHelloa (); }}classHellob { PublicHellob () {System.out.println ("I ' M B class"); }    Static{System.out.println ("Static B"); } {System.out.println (B); }}

Operation Result:

Static B
Static A
B
I ' M B class
A
I ' M A class

Parsing: Output order: Parent class static code block > Subclass Static code block > parent non-static code block > Parent class constructor > subclass non-static code block > Subclass constructor;

Java Common pen Questions < two >