title: Check that a String entered contains only 1's and 0's
body: <p>I am writing a program that switches a binary number into a decimal number and am only a novice programmer. I am stuck trying to determine that the string that was entered is a binary number, meaning it contains only 1's and 0's. My code so far is:</p>
  
  <pre><code>  String num;
    char n;
  
    Scanner in = new Scanner(System.in);
    System.out.println("Please enter a binary number or enter 'quit' to quit: ");
    num = in.nextLine();
    n = num.charAt(0);
    if (num.equals("quit")){
      System.out.println("You chose to exit the program.");
      return;
    }
  
    if (n != 1 || n != 0){
      System.out.println("You did not enter a binary number.");
    }
  </code></pre>
  
  <p>As is, no matter what is entered (other then quit) the program out-puts "You did not enter a binary number" even when a binary number is inputted. I am sure my if statement is false or my character declaration is wrong, however I have tried everything I personally know to correct the issue and nothing I find online helps. Any help would be appreciated.</p>