Implement Singleton Design Pattern in different Languages

Below are some code snippets which shows how to implement Singleton pattern.

Java

public class FileWriting {
    static private FileWriting _instance = null;   
    protected FileWriting(){
       
    }   
    static public FileWriting getInstance() {
      if(null == _instance) {
         _instance = new FileWriting();
      }
      return _instance;
    }
}

FileWriting javaObj = FileWriting.getInstance();


PHP

<?php
 class FileWriting{
    protected static $_instance;
    protected function __construct()
    {
       
    }
    public static function getInstance()
    {
        if(!self::$_instance)
        {  
            self::$_instance = new FileWriting();
        }
        return  self::$_instance;
    }
  } 
  phpObj = FileWriting::getInstance();
?>


Objective-C

@interface FileWriting : NSObject {
}
-(FileWriting*)getInstance;
@end

@implementation FileWriting
static FileWriting *_instance;
-(FileWriting*)getInstance{
   if(_instance==nil){
      _instance = [FileWriting alloc];
   }
   return _instance;
}
@end

Now to make an object of FileWriting interface.

FileWriting *objc_inst = [[FileWriting alloc] getInstance];