title: Java accepting only numbers from user with Scanner
body: <p>I am trying to understand how to only accept numbers from the user, and I have attempted to do so using try catch blocks, but I would still get errors with it.</p>
  
  <pre><code>    Scanner scan = new Scanner(System.in);
  
      boolean bidding;
      int startbid;
      int bid;
  
      bidding = true;
  
      System.out.println("Alright folks, who wants this unit?" +
              "\nHow much. How much. How much money where?" );
  
      startbid = scan.nextInt();
  
  try{
      while(bidding){
      System.out.println("$" + startbid + "! Whose going to bid higher?");
      startbid =+ scan.nextInt();
      }
  }catch(NumberFormatException nfe){
  
          System.out.println("Please enter a bid");
  
      }
  </code></pre>
  
  <p>I am trying to understand why it is not working.</p>
  
  <p>I tested it out by inputting a into the console, and I would receive an error instead of the hopeful "Please enter a bid" resolution.</p>
  
  <pre><code>Exception in thread "main" java.util.InputMismatchException
  at java.util.Scanner.throwFor(Scanner.java:909)
  at java.util.Scanner.next(Scanner.java:1530)
  at java.util.Scanner.nextInt(Scanner.java:2160)
  at java.util.Scanner.nextInt(Scanner.java:2119)
  at Auction.test.main(test.java:25)
  </code></pre>