Java Singleton.getInstance() returns null? -

I have this singleton that I am trying to use but can get apparently returning empty Are:

  class singleton {public static final string K_LEVEL = "level"; Stable singleton example = new singleton (); Private int level; Static singleton yield (return example;) int getLevel () {return level;} zero incrementLevel () {System.out.println ("increase in LEVEL" +++ level);} zero addToLevel (int x) {for (Int i = 0; i & lt; x; i ++) incrementLevel ();}} class A {public static zero main (string [] args) {singleton s = singleton.just instance (); integer i = integer GateInteger (singleton.kellev); s.addToLevel (i);}}   
 I have heard that singlantans in Java are very difficult to execute and run I am in danger of situations. Is my singleton pattern wrong? I have recently changed my code to look like this, and now why is instant return returns blank?   A- There is nothing wrong with your singleton: / div> 
 
 
 There are no concurrency problems because it is not a multithrred code.  < P> You were thinking that  s  was zero, but this is actually  i  this blank ./P> 
 Since  addToLevel  takes  int  as a parameter, therefore  integer I  was autounboxed (contained from  Integer  to  int ), but since  i  the  null ,  NullPointerException  was thrown off Was there. Autounboxing throws  NullPointerException  when the value is being hidden  null .  
 Reason  Integer.getInteger (Singleton.K_LEVEL)  Back  null  is because you have the  Java A-DelWell = 1  The opposite was  java -Delvel = 1 A . The latter is the correct syntax.