Here below a little program in Groovy that implements 2 classes (in fact, they are 3 + an extra utility Stopwatch class from my previous post http://carlosqt.blogspot.com/2011/05/stopwatch-class-for-java.html). There is the main class, called Fiborial (Fibo(nnacci)+(Facto)rial) that implements the Fibonacci and the Factorial algorithms in two ways, one Recursive (using recursion) and the other Imperative (using loops and states). The second class is just an instance class that does the same thing, but its there just to show the difference between static and instance classes, and finally the third one (which will not appear in other languages) is the Program class which has the static execution method "main".
You can also find 3 more little examples at the bottom. One prints out the Factorial's Series and Fibonacci's Series, the second one just shows a class that mixes both: static and instance members, and finally the third one that uses different return types (including java.math.BigInteger) for the Factorial method to compare the timing and result.
As with the previous posts, you can copy and paste the code below in your favorite IDE/Editor and start playing and learning with it. This little "working" program will teach you some more basics of the Programming Language.
There are some "comments" on the code added just to tell you what are or how are some features called. In case you want to review the theory, you can read my previous post, where I give a definition of each of the concepts mentioned on the code. You can find it here: http://carlosqt.blogspot.com/2011/01/new-series-factorial-and-fibonacci.html
The Fiborial Program
// Factorial and Fibonacci in Groovy
package com.series
import java.math.BigInteger
// Instance Class
class StaticFiborial
{
// Static Field
private static className
// Class/Static Constructor/Initializer
static
{
className = "Static Constructor"
println className
}
// Class/Static Method - Factorial Recursive
static factorialR(int n)
{
if (n == 1)
return BigInteger.ONE
else
return n * factorialR(n - 1)
}
// Class/Static Method - Factorial Imperative
static factorialI(int n)
{
def res = BigInteger.ONE
for (int i = n; i >= 1; i--)
{
res *= i
}
return res
}
// Class/Static Method - Fibonacci Recursive
static fibonacciR(int n)
{
if (n < 2)
return 1
else
return fibonacciR(n - 1) + fibonacciR(n - 2)
}
// Class/Static Method - Fibonacci Imperative
static fibonacciI(int n)
{
def pre, cur, tmp = 0
pre = cur = 1
for (i in 2..n)
{
tmp = cur + pre
pre = cur
cur = tmp
}
return cur
}
// Class/Static Method - Benchmarking Algorithms
static benchmarkAlgorithm(algorithm, values)
{
def timer = new Stopwatch()
def i, testValue
def facTimeResult = BigInteger.ZERO
def fibTimeResult = 0
i = testValue = 0
// "Switch" Flow Control Statement
switch (algorithm)
{
case 1:
println "\nFactorial Imperative:"
// "For" Loop Statement
for (i = 0; i < values.size(); i++)
{
testValue = ((Integer)values.get(i)).intValue()
// Taking Time
timer.start()
facTimeResult = factorialI(testValue)
timer.stop()
// Getting Time
println " ($testValue) = ${timer.getElapsed()}"
}
break
case 2:
println "\nFactorial Recursive:"
// "While" Loop Statement
while (i < values.size())
{
testValue = ((Integer)values.get(i)).intValue()
// Taking Time
timer.start()
facTimeResult = factorialR(testValue)
timer.stop()
// Getting Time
println " ($testValue) = ${timer.getElapsed()}"
i++
}
break
case 3:
println "\nFibonacci Imperative:"
// "For" Loop Statement
for (j in 0..values.size()-1)
{
testValue = ((Integer)values.get(j)).intValue()
// Taking Time
timer.start()
fibTimeResult = fibonacciI(testValue)
timer.stop()
// Getting Time
println " ($testValue) = ${timer.getElapsed()}"
}
break
case 4:
println "\nFibonacci Recursive:"
// "For Each" Loop Statement
for (item in values)
{
testValue = item
// Taking Time
timer.start()
fibTimeResult = fibonacciR(testValue)
timer.stop()
// Getting Time
println " ($testValue) = ${timer.getElapsed()}"
}
break
default:
println "DONG!"
break
}
}
}
// Instance Class
class InstanceFiborial
{
// Instance Field
private def className
// Instance Constructor
def InstanceFiborial()
{
this.className = "Instance Constructor"
println this.className
}
// Instance Method - Factorial Recursive
def factorialR(n)
{
// Calling Static Method
return StaticFiborial.factorialR(n)
}
// Instance Method - Factorial Imperative
def factorialI(n)
{
// Calling Static Method
return StaticFiborial.factorialI(n)
}
// Instance Method - Fibonacci Recursive
def fibonacciR(n)
{
// Calling Static Method
return StaticFiborial.fibonacciR(n)
}
// Instance Method - Factorial Imperative
def fibonacciI(n)
{
// Calling Static Method
return StaticFiborial.fibonacciI(n)
}
}
println "\nStatic Class"
// Calling Static Class and Methods
// No instantiation needed. Calling method directly from the class
println "FacImp(5) = ${StaticFiborial.factorialI(5)}"
println "FacRec(5) = ${StaticFiborial.factorialR(5)}"
println "FibImp(11)= ${StaticFiborial.fibonacciI(11)}"
println "FibRec(11)= ${StaticFiborial.fibonacciR(11)}"
println "\nInstance Class"
// Calling Instance Class and Methods
// Need to instantiate before using. Calling method from instantiated object
def ff = new InstanceFiborial()
println "FacImp(5) = ${ff.factorialI(5)}"
println "FacRec(5) = ${ff.factorialR(5)}"
println "FibImp(11)= ${ff.fibonacciI(11)}"
println "FibRec(11)= ${ff.fibonacciR(11)}"
// Create a list of integer values to test
// From 5 to 50 by 5
def values = []
5.step(55, 5) {
values.add(it)
}
// Benchmarking Fibonacci
// 1 = Factorial Imperative
StaticFiborial.benchmarkAlgorithm(1, values)
// 2 = Factorial Recursive
StaticFiborial.benchmarkAlgorithm(2, values)
// Benchmarking Factorial
// 3 = Fibonacci Imperative
StaticFiborial.benchmarkAlgorithm(3, values)
// 4 = Fibonacci Recursive
StaticFiborial.benchmarkAlgorithm(4, values)
// Stop and exit
println "Press any key to exit..."
def sin = new Scanner(System.in)
def line = sin.nextLine()
sin.close()
And the Output is:
Printing the Factorial and Fibonacci Series
package com.series
import java.math.BigInteger
import java.lang.StringBuffer
class Fiborial
{
// Using a StringBuffer as a list of string elements
static getFactorialSeries(n)
{
// Create the String that will hold the list
def series = new StringBuffer()
// We begin by concatenating the number you want to calculate
// in the following format: "!# ="
series.append("!")
series.append(n)
series.append(" = ")
// We iterate backwards through the elements of the series
for (i in n..0)
{
// and append it to the list
series.append(i)
if (i > 1)
series.append(" * ")
else
series.append(" = ")
}
// Get the result from the Factorial Method
// and append it to the end of the list
series.append(factorial(n))
// return the list as a string
return series
}
// Using a StringBuffer as a list of string elements
static getFibonnaciSeries(n)
{
// Create the String that will hold the list
def series = new StringBuffer();
// We begin by concatenating the first 3 values which
// are always constant
series.append("0, 1, 1")
// Then we calculate the Fibonacci of each element
// and add append it to the list
for (i in 2..n)
{
if (i < n)
series.append(", ")
else
series.append(" = ")
series.append(fibonacci(i))
}
// return the list as a string
return series
}
static factorial(n)
{
if (n == 1)
return BigInteger.ONE
else
return n * factorial(n - 1)
}
static fibonacci(n)
{
if (n < 2)
return 1
else
return fibonacci(n - 1) + fibonacci(n - 2)
}
}
// Printing Factorial Series
println ""
println Fiborial.getFactorialSeries(5)
println Fiborial.getFactorialSeries(7)
println Fiborial.getFactorialSeries(9)
println Fiborial.getFactorialSeries(11)
println Fiborial.getFactorialSeries(40)
// Printing Fibonacci Series
println ""
println Fiborial.getFibonnaciSeries(5)
println Fiborial.getFibonnaciSeries(7)
println Fiborial.getFibonnaciSeries(9)
println Fiborial.getFibonnaciSeries(11)
println Fiborial.getFibonnaciSeries(40)
And the Output is:
Mixing Instance and Static Members in the same Class
Instance classes can contain both, instance and static members such as: fields, getters/setters, constructors/initializers, methods, etc.
package com.series
// Instance Class
class Fiborial
{
// Instance Field
private def instanceCount
// Static Field
private static staticCount
// Instance Read-Only Getter
// Within instance members, you can always use
// the "this" reference pointer to access your (instance) members.
def getInstanceCount()
{
return this.instanceCount
}
// Static Read-Only Getter
// As with Static Methods, you cannot reference your class members
// with the "this" reference pointer since static members are not
// instantiated.
static getStaticCount()
{
return staticCount
}
// Instance Constructor
def Fiborial()
{
this.instanceCount = 0
println "\nInstance Constructor ${this.instanceCount}"
}
// Static Constructor
static
{
staticCount = 0;
println "\nStatic Constructor $staticCount"
}
// Instance Method
def factorial(n)
{
this.instanceCount += 1
println "\nFactorial($n)"
}
// Static Method
static fibonacci(n)
{
staticCount += 1
println "\nFibonacci($n)"
}
}
// Calling Static Constructor and Methods
// No need to instantiate
Fiborial.fibonacci(5)
// Calling Instance Constructor and Methods
// Instance required
def fib = new Fiborial()
fib.factorial(5)
Fiborial.fibonacci(15)
fib.factorial(5)
// Calling Instance Constructor and Methods
// for a second object
def fib2 = new Fiborial()
fib2.factorial(5)
println ""
// Calling Static Property
println "Static Count = ${Fiborial.getStaticCount()}}"
// Calling Instance Property of object 1 and 2
println "Instance 1 Count = ${fib.getInstanceCount()}"
println "Instance 2 Count = ${fib2.getInstanceCount()}"
And the Output is:
Factorial using java.lang.Long, java.lang.Double, java.math.BigInteger
package com.series
import java.math.BigInteger
// Long Factorial
long factorialInt64(n)
{
if (n == 1)
return 1
else
return n * factorialInt64(n - 1)
}
// Double Factorial
double factorialDouble(n)
{
if (n == 1)
return 1
else
return n * factorialDouble(n - 1)
}
// BigInteger Factorial
BigInteger factorialBigInteger(n)
{
if (n == 1)
return BigInteger.ONE
else
return n * factorialBigInteger(n - 1)
}
def timer = new Stopwatch()
long facIntResult = 0
double facDblResult = 0
def facBigResult = BigInteger.ZERO
println "\nFactorial using Int64"
// Benchmark Factorial using Int64
for (i in (5..50).step(5)) {
timer.start()
facIntResult = factorialInt64(i)
timer.stop()
println " ($i) = ${timer.getElapsed()} : ${facIntResult}"
}
println "\nFactorial using Double"
// Benchmark Factorial using Double
for (i in (5..50).step(5)) {
timer.start()
facDblResult = factorialDouble(i)
timer.stop()
println " ($i) = ${timer.getElapsed()} : ${facDblResult}"
}
println "\nFactorial using BigInteger"
// Benchmark Factorial using BigInteger
for (i in (5..50).step(5)) {
timer.start()
facBigResult = factorialBigInteger(i)
timer.stop()
println " ($i) = ${timer.getElapsed()} : ${facBigResult}"
}
And the Output is:
