LOTUSSCRIPT LANGUAGE

LS2J extended example
This sample code demonstrates calling Java methods within LotusScript using LS2J. Immediately following this example the code is modified slightly to demonstrate handling situations where there is a syntax discrepancy between Java and LotusScript.

Mortgage Calculator

With this mortgage calculator you can get the value of a Java property and call several Java methods by using the names directly from LotusScript.

Mortgage.java
public class Mortgage

{

   // Java property

   public static String F = "Mortgage Calculator";

   // Java methods

   public double CalculateInterest(float rate, short yr, _

double principal)

   {

// This bank doesn't bother with compound interest!

return (rate / 100) * yr * principal;

   }

   public double CalculateTotal(double principal, _
   double interest)

   {

return principal + interest;

   }

   public double CalculateMonthlyPayment(float rate, _
  short yr, double principal)

   {

double interest = CalculateInterest(rate, yr, _
    principal);

double total = CalculateTotal(principal, interest);

return total / (yr * 12);

   }

}

Mortgage.lss
Uselsx "*javacon"

Dim mySession As JavaSession

Sub Initialize

Dim myClass As JavaClass

Dim myObject As JavaObject

Dim header As String

Dim rate As Single

Dim yr As Integer

Dim principal As Double, interest As Double

Dim total As Double, monthly_payment As Double

Set mySession = New JavaSession()

' Set LS values

rate = 8.5

yr = 30

principal = 200000

Set mySession = New JavaSession()

' Get Java "Mortgage" class

Set myClass = mySession.GetClass("Mortgage;")

' Call Java "Mortgage" Constructor

Set myObject = myClass.CreateObject

' Get Java property (can just use the name)

header = myObject.F

' Call Java Methods (can just use the names)

interest = myObject.CalculateInterest(rate, yr, _
    principal)

total = myObject.CalculateTotal(principal, interest)

monthly_payment = _
    myObject.CalculateMonthlyPayment(rate, yr, principal)

MsgBox { } & header & {

Interest rate:   } & rate & {%

Years:            } & 30 & {

Principal:       $} & principal & {

Interest:        $} & Round(interest, 2) & {

Total:            $} & Round(total, 2) & {

Monthly payment: $} & Round(monthly_payment, 2)

End Sub

Mortgage Calculator (Version 2)

In this example, a few problems with syntax have been introduced:


These types of syntax are allowed in Java but not in LotusScript. "Mortgage2.lss" shows how to use LS2J in this situation. At the end is an example of trapping a JavaError.

Mortgage2.java
public class Mortgage2

{

   // Java properties with names that differ only by case

   public static String F = "Mortgage Calculator";

   public static String f = "from your friendly neighborhood bank";

   // Java methods

   // Two Java methods with names that differ only by case

   public double calculateinterest(float rate, _
  short yr, double principal)

   {

  return rate * yr * principal;

}

   public double CalculateInterest(float rate, _
  short yr, double principal)

   {

  return calculateinterest(rate/100, yr, principal);

   }

   // Method with a long name

   public double

CalculateTotal_with_a_method_name_over_40_characters_long

(double principal, double interest)

   {

  return principal + interest;

   }

   // Two Java overloaded methods -- differ only by parameter types

   public double CalculateMonthlyPayment(double total, short yr)

   {

  return total / (yr * 12);

   }

   public double CalculateMonthlyPayment(float rate, short yr, _

double principal)

   {

double interest = CalculateInterest(rate, yr, principal);

double total =

CalculateTotal_with_a_method_name_over_40_characters_long

(principal, interest);

return CalculateMonthlyPayment(total, yr);

   }

}

Mortgage2.lss
Uselsx "*javacon"

Dim mySession As JavaSession

Sub Initialize

Dim myClass As JavaClass

Dim myObject As JavaObject

Dim myProperty As JavaProperty

Dim myMethod As JavaMethod

Dim myError As JavaError

Dim header1 As String, header2 As String

Dim rate As Single

Dim yr As Integer

Dim principal As Double, interest As Double

Dim total As Double, monthly_payment As Double

Set mySession = New JavaSession()

' Set LS values

rate = 8.5

yr = 30

principal = 200000

Set mySession = New JavaSession()

Set myClass = mySession.GetClass("Mortgage2;")

' Call "Mortgage2" constructor

Set myObject = myClass.CreateObject

' Use GetProperty()/GetValue() syntax when

' property names differ only by case

Set myProperty = myClass.GetProperty("F")

header1 = myProperty.GetValue()

Set myProperty = myClass.GetProperty("f")

header2 = myProperty.GetValue()

' Use GetMethod()/Invoke() syntax when method

' names differ only by case

Set myMethod = _
     myClass.GetMethod("CalculateInterest", "(FSD)D")

interest = myMethod.Invoke(myObject, rate, yr, _
     principal)

' or when method name is over 40 characters long

Set myMethod = myClass.GetMethod  _

("CalculateTotal_with_a_method_name_over_40_characters_long", _

"(DD)D")

total = myMethod.Invoke(myObject, principal, interest)

' or for overloaded Methods (differing only by parameter type)

Set myMethod = _
     myClass.GetMethod("CalculateMonthlyPayment", "(DS)D")

monthly_payment = _
     myObject.CalculateMonthlyPayment(total, yr)

MsgBox { } & header1 & {

} & header2 & {

Interest rate:   }   & rate & {%

Years:            } & 30 & {

Principal:       $} & principal & {

Interest:        $} & Round(interest, 2) & {

Total:            $} & Round(total, 2) & {

Monthly payment: $} & Round(monthly_payment, 2)

On Error GoTo errhandler

' Throws "java.lang.NoSuchMethodException"

' when user tries to get a method that doesn't exist

Set myMethod = myClass.GetMethod("CalculateTax", _
     "(D)D")

done:

Exit Sub

errhandler:

Set myError = mySession.GetLastJavaError()

MsgBox "JavaError was " & myError.errorMsg

' Clear the Error

mySession.ClearJavaError

Resume done

End Sub

See Also