Java - Coordenadas de inicio y de final de una recta

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package recursividad;

import java.util.Scanner;

/**

 *

 * @author User

 */

public class ayuda {

     static Scanner s = new Scanner (System.in);

        public static void main(String[] args) {

            System.out.println("ingrese coordenada x1:");

            int x1= s.nextInt();

            System.out.println("ingrese coordenada Y1:");

            int y1= s.nextInt();

            System.out.println("ingrese coordenada x2:");

            int x2= s.nextInt();

            System.out.println("ingrese coordenada Y2:");

            int y2= s.nextInt();

            mostrar(x1,y1,x2,y2);

        }

    private static void mostrar(int x1, int y1, int x2, int y2) {

        if(x1<x2){

      for(int a=x1; a<x2+1;a++){

          System.out.println(a+","+y1);

          y1=y1+1;

      }

          }

        else{

             for(int a=x1; a>x2-1;a--){

          System.out.println(a+","+y1);

          y1=y1-1;

      }

        }

    }

}