Groovy example source code file (MortgageCalculator.groovy)

This example Groovy source code file (MortgageCalculator.groovy) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Groovy tags/keywords

amount, amount, annual, annual, calculator, loan, loan, monthly, monthly, mortgage, please, this

The Groovy MortgageCalculator.groovy source code

/** 
 * Mortgage Calculator
 * @author: Jeremy Rayner
 * based on algorithms by Jeff Louie, Dr W Carlini and Newton
 */

println "__..::~~'''~~::..__"
println "Mortgage Calculator"
println "~~~~~~~~~~~~~~~~~~~"
println "Please input 3 of the 4 values in your mortgage calculation"
println "This program will then calculate the value you leave blank"
println ""

def variables = [
    "Amount of mortgage" : 0.0, 
    "Annual interest rate (%)" : 0.0, 
    "Loan duration (months)" : 0.0, 
    "Monthly payments" : 0.0
]

for (entry in variables.entrySet()) {
    print("${entry.key}:")
    def userInput = System.in.readLine()
    if ("" == userInput) {
        valueToCalculate = entry.key
    } else {
        entry.value = userInput.toDouble()
    }
}

println "$valueToCalculate = ${calculateValueOf(valueToCalculate)}"





def calculateValueOf(valueToCalculate) {
    def result = 0
    def principal = variables["Amount of mortgage"]
    def interest = variables["Annual interest rate (%)"] / 1200
    def months = variables["Loan duration (months)"]
    def payment = variables["Monthly payments"]

    switch (valueToCalculate) {
    case "Amount of mortgage":
        result = 1 + interest
        result = 1/Math.pow(result,months)
        result = ((1-result)/interest) * payment
        break           
    case "Loan duration (months)":
        result = (1 - (principal * interest / payment))
        result = Math.log(result)
        result = - result / Math.log(1 + interest)  
        break
    case "Monthly payments":
        result = 1 + interest
        result = 1 / Math.pow(result,months)
        result = (principal * interest) / (1 - result)
        break          
    case "Annual interest rate (%)":
        result = payment / principal
        def diff = 100; def accuracy = 0.00001; def maxIterations = 1000
        def index = 0
        while ((diff > accuracy) && (index < maxIterations)) {
            def temp = result
            def numerator = (principal * temp / payment) + Math.pow((1 + temp), -months) - 1
            def denominator= (principal / payment) - months * Math.pow((1 + temp), (-months - 1))
            result = temp - (numerator / denominator)
            diff = result - temp
            diff = Math.abs(diff)
            index++
        }
        result *= 1200
        break           
    }
    return result
}