Code for debounce button

const int LED=9 ;
const int BUTTON=2 ;
boolean lastButton = LOW;
boolean currentButton = LOW;
boolean ledOn = false;
void setup ()
{
  pinMode (LED, OUTPUT) ;
  pinMode (BUTTON, INPUT) ;
}
boolean debounce (boolean last)
{
  boolean current = digitalRead (BUTTON) ;
  if (last != current)
  {
    delay(5) ;
    current = digitalRead (BUTTON) ;
  }
  return current ;
}
void loop( )
{
  currentButton = debounce(lastButton) ;
  if (lastButton == LOW && currentButton == HIGH)
  {
    ledOn = !ledOn ;
  }
  lastButton = currentButton;
  digitalWrite (LED, ledOn) ;
}