title: Exception in thread "main" java.util.InputMismatchException
body: <p>I`m MAC user and
  I have been struggling with this error. 
  I search this error, now I just can't find solutions. </p>
  
  <pre><code>Exception in thread "main" java.util.InputMismatchException
  at java.util.Scanner.throwFor(Scanner.java:864)
  at java.util.Scanner.next(Scanner.java:1485)
  at java.util.Scanner.nextInt(Scanner.java:2117)
  at java.util.Scanner.nextInt(Scanner.java:2076)
  at GradeBook.inputGrades(GradeBook.java:53)
  at GradeBookTest.main(GradeBookTest.java:12)
  </code></pre>
  
  <p>It is Not a problem of the variable, 
  and the code written As recorded in the book .</p>