How to execute a static block for multiple times in java

Question

I have given a task to execute static block for every 20 seconds. I have a class that consists of a static block.

public class Hello{
      static{
        System.out.println("helloo...");
      }
}

I know that static block executes when the class is loaded.

But i want to know is there any way to execute the static block for multiple times and how?

static block get executed when class is loaded, if you want multiple times use method — Ryuzaki L, Oct 03 '18 at 14:27
They question is, why do you want to do this? Static blocks cannot do this. How about adding the code as a static method and running the method as many times as needed? — blurfus, Oct 03 '18 at 14:27
You can't, unless your class is loaded by multiple classloaders. It will be executed once per classloader, when either an instance of `Hello` is initialized or a static method of `Hello` is invoked. — Mena, Oct 03 '18 at 14:28
I have clearly addressed my problem here that i have to specifically do like this yet this question has 6 downvotes. — Prudhvi Bellam, Sep 27 '19 at 06:42

score 2 · Accepted Answer · answered Oct 04 '18 at 12:37

Executing a Static Block can be Achieved by using Custom Class Loader.

ClassReload.java

    Class<?> load = ClassLoader.getSystemClassLoader().loadClass("com.Hello");
//Assume Hello class is in "com" package 
        load.newInstance().toString();
        URL[] urls = { load.getProtectionDomain().getCodeSource().getLocation() };
        ClassLoader delegateParent = load.getClassLoader().getParent();
        try (URLClassLoader cl = new URLClassLoader(urls, delegateParent)) {
            Class<?> reloaded = cl.loadClass(load.getName());
            reloaded.newInstance().toString();              
            }
            }
        }

Refer Oracle Document for URLClassLoader

score 0 · Answer 2 · answered Oct 03 '18 at 14:26

0

Static block runs when class loads, You can't run it multiple time.

answered Oct 03 '18 at 14:26

Rahim Dastar

1,259
1
9
15

what if i unload and load it again? – Prudhvi Bellam Oct 03 '18 at 14:44
Look at this: https://stackoverflow.com/questions/148681/unloading-classes-in-java – Rahim Dastar Oct 07 '18 at 08:50
Actually, i found the solution with urlclassloader. Thanks – Prudhvi Bellam Oct 08 '18 at 05:37

score 0 · Answer 3 · answered Oct 03 '18 at 14:29

Like any other block of code that you want to execute several times you can use a loop or better to create a static function and call it several times:

public class Hello{
    public static void hello() {
        System.out.println("helloo...");
    }

    public void someMethod() {

        for(int i= 0; i < 10; i++) {
            hello();
        }
     }
}

score 0 · Answer 4 · answered Oct 03 '18 at 14:31

0

You cannot. It will be run only once, when class is loads. There is one more chance you can write any number of static block in a class.

[https://beginnersbook.com/2013/04/java-static-class-block-methods-variables/][1]

answered Oct 03 '18 at 14:31

arjunan

217
1
9

How to execute a static block for multiple times in java

4 Answers4