title: java.lang.NullPointerException with boolean
body: <p>I wrote a realy simple code based on another question and here it is:</p>
  
  <p>It throws me an error</p>
  
  <blockquote>
    <p>java.lang.NullPointerException line 5 and 17</p>
  </blockquote>
  
  <p>I don't know what I'm doing wrong.</p>
  
  <pre><code> public class Main {
  
      public static String bool(Boolean param){
          if(param == true){    (line 5)
              return "a";
          }else if(param == false){
              return "b";
          }
          return "c";
  
      }
  
      public static void main(String[] args){
  
          System.out.println(bool(true));
          System.out.println(bool(null)); (line 17)
          System.out.println(bool(false));
  
  
      }
  }
  </code></pre>