As of the series make a return value?

Good day !
Write code for the game TIC/TAC toe at the moment trying to write a test win. The question arose.
There is a method performs ( in this case vertical) as I from this method to return the alternate value, provided that the cycle should not stop checking. When I write return in a loop, it interrupts its action, which is not suitable for my case, because then it does not check all verticals( and only first). I enclose a piece of code.

public String checkVertical (Field field){
 Point point1 = new Point(); //object creation figures
 Point point2 = new Point(); //object creation figures
 Point point3 = new Point(); //object creation figures
 String x = null; //variable which will return for a final check of the winner
 for (int i = 0; i < field.getSize(); i++){
 //check the coordinates
 point1.x = i; 
 point2.x = i;
 point3.x = i;
 point1.y = 0;
 point2.y = 1;
 point3.y = 2;
 x = checkThreePoint(point1, point2, point3, field) ; // this method checks the figures on the coincidence(if there is 3 of 3 the winner is returned, otherwise null
 if (x != null) {
 return x; //this check stops the loop that is incorrect
}
 else{ 
 return null;
}
}
 return x; // here should return the final winner
 }