Est Communication among helper classes and the main class

I'm just learning programming concepts in Java 2 and don't understand how to put my "program" together so that both classes exist and work together to produce some mock invoices. I checked my classpath - fine and both files were saved in the same directory. And I don't see any typos...

I have two classes: Smith_Week3_InvoiceItem.java has my set/get functions to hold my invoice items (which compiles fine) The "main" class is my Smith_Week3_CreateInvoice.java (which is a mess and does not exist...I get the dreaded cannot resolve symbol and am sure it is a simple thing I've overlooked...) Anyway, I have to resolve this before I can get my main class to print my items. I don't get how it will call the methods to the other class...

No laughing - code so far:

//*Make class public so that all other classes can see it (ie: CreateInvoice)
public class Smith_Week3_InvoiceItem
{
  //Constructors

  public Smith_Week3_InvoiceItem()
  {
    //Call to new method
    reset();

    return;
  }
  //constructor: taking all arguments
  public Smith_Week3_InvoiceItem(String itemNameIn, int itemIdIn, float itemCostIn)
  {
    set(itemNameIn, itemIdIn, itemCostIn);

    return;
  }

  //Misc functions

 //set all args at once

  public void set(String itemNameIn, int itemIdIn, float itemCostIn)
  {
    setItemName(itemNameIn);
    setItemId(itemIdIn);
    setItemCost(itemCostIn);

    return;
  }

  //Reset all args to default values
  public void reset()
  {
    setItemName("");
    setItemId(0);
    setItemCost(0.0f);

    return;
}

//Create a string containing all of the cureent values
public String toString()
{
      String outputString = "Smith_Week3_InvoiceItem: Name=" + getItemName() + "; Id=" + getItemId() + "; Cost=" + getItemCost();

      return outputString;
}

  //Do set/get functions
  //Don't allow null balues for strings
  //Don't allow negative values for prices
  //Id numbers must be > 0
public void setItemName(String valueIn)
{
      if(valueIn !=null)
      {
            itemName=valueIn;
    }
    return;
}
public String getItemName()
{
    return itemName;
}

public void setItemId(int valueIn)
{
      if(valueIn > 0)
      {
            itemId=valueIn;
    }
    return;
}
public int getItemId()
{
      return itemId;
}
public void setItemCost(float valueIn)
{
      if(valueIn >=0.0f)
      {
            itemCost=valueIn;
    }
    return;
}
public float getItemCost()
{
      return itemCost;
}

//Do member data/attributes

private String itemName = "";
private int itemId = (0);
private float itemCost = 0.0f;

}//End of class Smith_Week3_InvoiceItem


The other class:

public class Smith_Week3_CreateInvoice
{
      public static void main(String[] args)
      {
            //Create some new invoices
            Smith_Week3_Invoice invoice1 = new Smith_Week3_Invoice("Palm m505", 1, 125.50f);
            Smith_Week3_Invoice invoice2 = new Smith_Week3_Invoice("Dell Laptop", 2, 1800.00f);
            Smith_Week3_Invoice invoice3 = new Smith_Week3_Invoice("Sony Digital Camera", 3500.00f);

            //Print out the information for each invoice
            System.err.println("Invoice 1:"+ invoice1.toString());
            System.err.println("Invoice 2:"+ invoice2.toString());
            System.err.println("Invoice 3:"+ invoice3.toString());

            //Print out the information for each invoice
            float totalValue = invoice1.getItemCost() + invoice2.getItemCost() + invoice3.getItemCost();
            System.err.printIn("Total value: $" + totalValue);
      }
}

If you could point me in the right direciton - I would be greatful      -Frustrated!