Java Eclipseコンソールは、ユーザー入力の値と文字列値を比較する前にプログラムを終了します

だから私は弟のためにこのプログラムを作っているのですが、問題にぶつかりました。プログラムは、ユーザーの入力を要求し、一連の「if」ステートメントを介してそれを複数の文字列値と比較することを想定しています。代わりに、ユーザーが入力を入力すると、プログラムが即座に終了します。私はこれに何時間もいて、それについてかなりくすぐられ始めています。これまでに入力したコードは次のとおりです。

package package1;
import java.util.Scanner;

public class Psychic_Calculator {
@SuppressWarnings("resource")
public static void main(String[] args) {

Scanner scan = new Scanner(System.in);  
System.out.println("Hello user, please type your name below:"); 
String a = scan.nextLine();
System.out.println("Welcome " + a + ", think of a number. Once you have your  number, type 'okay' below!");

String b = scan.nextLine();

if (b == "okay"){

System.out.println("Now, add '11' to your number and type 'okay' below.");
    }

else if (b == "Okay"){

System.out.println("Please don't capitalize 'okay', try typing it again!");

String c = scan.nextLine();

if (c == "okay"){

System.out.println("Now, add '11' to your number and type 'okay' below.");

String d = scan.nextLine();

if (d == "okay"){

System.out.println("Now, add '2' to your new number, then type 'okay' below.");

String e = scan.nextLine();

if (e == "okay"){

System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");

String f = scan.nextLine();

if (f == "okay"){

System.out.println("Your new number is '13'. Don't even try denying it.");
                    }
                }
            }
        }

        if (c == "Okay"){

        System.out.println("I already told you not to capitalize 'okay', try typing it again, you idiot!");

        String g = scan.nextLine();

        if (g == "okay"){

        System.out.println("Now, add '11' to your number and type 'okay' below.");

        String h = scan.nextLine();

        if (h == "okay"){

        System.out.println("Now, add '2' to your new number, then type 'okay' below.");

        String i = scan.nextLine();

        if (i == "okay"){

        System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");

        String j = scan.nextLine();

        if (j == "okay"){

        System.out.println("Your new number is '13'. Don't even try denying it.");  
                        }
                    }
                }
            }
        }

        if (c != "okay") {

        while (c != "okay") {

        System.out.println("Do you even know how to spell 'okay'?" + "'" + c + "' does not spell 'okay', you moron! Try typing 'okay' again.");

        String n = scan.nextLine();

        if (n == "okay"){

        System.out.println("Finally, you learned how to spell 'okay'. Your vocabulary is now one word larger, you're welcome. Now, please add '11' to your number and then type 'okay'(correctly this time).");

        String k = scan.nextLine();

        if (k == "okay"){

        System.out.println("Now, add '2' to your new number, then type 'okay' below.");

        String l = scan.nextLine();

        if (l == "okay"){

        System.out.println("Now, subtract your original number from your new number, then type 'okay' below.");

        String m = scan.nextLine();

        if (m == "okay"){

        System.out.println("Your new number is '13'. Don't even try denying it.");  
                }

                }
            }

        }

        else {
            System.out.println(a + ", " + "you have failed to type 'okay' too many times! You have no idea how to spell 'okay' you electricutin' motherboarder! Go shove your face in a pile of computer chips and grow a pair!");

                    System.out.println("(of RAM cartriges...I meant to say RAM cartriges).");
                }   
             }
          }
       }
    }
}