How do I make my If Statement not jump to else?

Question

My java if statement is not working as expected. When the end user answers the question in either yes or no, I want that answer to drive the output from the if/else statement. However, no matter what the answer is, the code jumps to the else piece. What am I doing wrong?

public void door() {
    
    Scanner keyboard = new Scanner(System.in);
    System.out.print("Is the mailbox door open (yes or no)?");
    String door = keyboard.next();
    this.door = door.toUpperCase();
    
    this.door = "YES";
    this.door = "NO";
    
    String open = "You should close the mailbox door!";
    String close = "The mailbox door is closed.";
    
    if (this.door == "YES") {
        System.out.println(open);
    }
        else
        System.out.println(close);
    
}