Trying to use If-else-If on a Scanner Input, won't print properly [duplicate]

I'm a relatively new Java student, and I was recently trying to mix the scanner tool with if-else-if. Every time I try to run the program and I input M,m,F, or f, I run into my last "else" where it ends the program and tells me that my input is invalid

    System.out.print("Please enter your gender (M/F): ");
    String Gender = in.nextLine();
    
    if ((Gender == "M") || (Gender == "m"))
        System.out.println("MALE");
    else if ((Gender == "F") || (Gender == "f"))
        System.out.println("FEMALE");
    else 
        {
        System.out.println("");
        System.out.println("Invalid Input For Gender!");
        System.out.println("Please Try Again!");
        System.exit(0);
        }