Je ne comprends pas ce b*rdel

package me.fr.killuaah;

import java.util.Scanner;

public class Main {

 public static void main(String[] args) {
  // TODO Auto-generated method stub
   System.out.println("----------Calculator v1 by Killuaah----------");
    System.out.println("Please enter a number");
    //Début du get du n1
    long n1;
    Scanner num1 = new Scanner(System.in);
   n1 = num1.nextLong();
   //Fin du get du n1 
   System.out.println("Please enter a second number");
    
   //Début du get du n2
   long n2;
   Scanner num2 = new Scanner(System.in);
   n2= num2.nextLong();
   //Fin du get du n2
   System.out.println("Please enter + or -");
   
   //Début du get de l'opération
   String op;
   Scanner ope = new Scanner(System.in);
   op = ope.nextLine();
   //Fin du get de l'opération 
   
   //+
   if (op == "+")
   {
   long result = n1 + n2;
   System.out.print(+ n1);
   System.out.print("+");
   System.out.print(+ n2);
   System.out.print("=");
   System.out.print(+result);
   
   }
   //Fin +
   
    
   else if (op == "-");

   {
    long result = n1 - n2;
    System.out.print(+ n1);
    System.out.print("-");
    System.out.print(+n2);
    System.out.print("=");
    System.out.print(+ result);
    result = 0;
   }
   return;
 
 
 
 
 }

}