The static method in a class can be called without an instance but via the direct class name.

Here is the implementation in Scala:

 object Foo {
   var int = 0
   def increase = { int += 1; int }
 }
   
 println(Foo.increase)
 println(Foo.increase)
 println(Foo.increase)
 

The run results:

 $ scala t2.scala 
 1
 2
 3
 

This is Ruby code for which I don't know if it's best written but it does work.

 class Foo
   def self.count
     @x ||= 0
     @x += 1
     @x
   end
 end
   
 puts Foo.count
 puts Foo.count
 puts Foo.count
 

And the last is Perl code.

 use strict;
 use warnings;
   
 package A;
   
 sub count {
   our $int ||= 0;
   $int ++;
   return $int;
 }
   
 1;
   
 package B;
   
 print A->count,"\n";
 print A->count,"\n";
 print A->count,"\n";
 

For this implementation, perl and ruby are similar. They require to define a global variable for holding that increment value. Though both perl and ruby community don't suggest you to use a global variable.

IIRC perl calls this as a closure, while scala and ruby call it as singleton.

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