title: Connecting main class to other classes
body: <p>I am writing a program in java were I have to make a class (InvoiceTest) that will have main in it and a second class (Invoice). When I run the main InvoiceTest class it should show the message in the Invoice class. I keep getting an error </p>
  
  <pre><code>Exception in thread "main" java.lang.ExceptionInInitializerError
      at InvoiceTest.main(InvoiceTest.java:4)
  Caused by: java.lang.RuntimeException: Uncompilable source code - constructor Invoice() is already defined in class Invoice
      at Invoice.&lt;clinit&gt;(Invoice.java:20)
      ... 1 more
  </code></pre>
  
  <p>I dont know what to do, please let me know what I am doing wrong and any suggestions on how to fix it. Thanks</p>
  
  <pre><code>public class InvoiceTest{
      public static void main(String [] args) {
          Invoice invoiceObject = new Invoice();
          invoiceObject.simpleMessage();
      }
  }
  
  // This is the second class. I am using NetBeans so each class is in its own window.
  
  public class Invoice {        
      public void simpleMessage() {
          System.out.println("This is another class");
      }
  }
  </code></pre>