Lesson 2: User Interfaces Revisited

The int data type contains a single whole 32-bit integer value that can be positive or negative. You can use the standard arithmetic operators (+, -, *, and /) to perform arithmetic operations on the integer.

The Integer class, not only contains a whole 32-bit integer value that can be positive or negative, but provides methods for working on the value. For example, the Integer.intValue method lets you convert an Integer to an int to perform arithmetic operations.

The double data type contains a 64-bit double-precision floating point value. The Double class not only contains a 64-bit double-precision floating point value, but provides methods for working on the value. for example, the Double.doubleValue method lets you convert a Double to a double to perform arithmetic operations.

Server Program Code

The server program consists of the RemoteServer.java class that implements the methods declared in the Send.java interface. These classes are described in Part 1, Lesson 8: Remote Method Invocation with the only difference being in this lesson there are many more sendXXX and getXXX methods to declare and implement. Here is the list:

• public void sendCreditCard(String creditcard){cardnum = creditcard;}
• public String getCreditCard(){return cardnum;}
• public void sendCustID(String cust){custID = cust;}
• public String getCustID(){return custID;}
• public void sendAppleQnt(String apps){apples = apps;}
• public String getAppleQnt(){return apples;}
• public void sendPeachQnt(String pchs){ peaches = pchs;}
• public String getPeachQnt(){return peaches;}
• public void sendPearQnt(String prs){pears = prs;}
• public String getPearQnt(){return pears;}
• public void sendTotalCost(double cst){cost = cst;}
• public double getTotalCost(){return cost; }
• public void sendTotalItems(int itm){items = itm;}
• public int getTotalItems(){return items;}

The important thing to note is data of any type and size can be easily passed from one client through the server to another client using the RMI API. No special handling is needed for large amounts of data or special considerations for different data types, which can sometimes be issues when using socket communications.

View Order Client Code

The OrderClient.java class uses text areas and buttons to display the order information.

The code is very similar to the FruitOrder.java class so rather than repeat much of what you have read above, this section highlights two parts of the actionPerformed method behavior for viewing an order.

The first part retrieves the credit card number, and the number of apples, peaches, and pears ordered from the server and sets those values in the corresponding text areas.

The second part retrieves the cost and item totals, which are double and integer, respectively. It then converts the total cost to a java.lang.Double object, and the total items to a java.lang.Integer object, and calls the toString method on each to get the string equivalents. Finally, the strings can be used to set the values for the corresponding text areas.

if(source == view){
 try{
//Retrieve and display text
  text = send.getCreditCard();
  creditNo.setText(text);

  text = send.getCustID();
  customerNo.setText(text);

  text = send.getAppleQnt();
  applesNo.setText(text);

  text = send.getPeachQnt();
  peachesNo.setText(text);

  text = send.getPearQnt();
  pearsNo.setText(text);

//Convert Numbers to Strings
  cost = send.getTotalCost();
  price = new Double(cost);
  unit = price.toString();
  icost.setText(unit);

  items = send.getTotalItems();
  itms = new Integer(items);
  i = itms.toString();
  itotal.setText(i);

 } catch (Exception e) {
  System.out.println("Cannot send data to server");
 }
}