Added exceptions to the factorial functions

src/main/java/mattrixwv/Algorithms.java

@@ -26,6 +26,7 @@ package mattrixwv;
 
 
 import java.math.BigInteger;
+import java.security.InvalidParameterException;
 import java.util.ArrayList;
 import java.util.Collections;
 
@@ -626,10 +627,13 @@ public class Algorithms{
 		return fibNums;
 	}
 	//This function returns the factorial of the number passed to it
-	public static Integer factorial(Integer num){
+	public static Integer factorial(Integer num) throws InvalidParameterException{
 		Integer fact = 1;	//The value of the factorial
 
-		//TODO: Throw an exception for values < 0
+		//If the number passed in is < 0 throw an exception
+		if(num < 0){
+			throw new InvalidParameterException("n! cannot be negative");
+		}
 		//Loop through every number up to and including num and add the product to the factorial
 		for(Integer cnt = 2;cnt.compareTo(num) <= 0;++cnt){
 			fact *= cnt;
@@ -637,9 +641,13 @@ public class Algorithms{
 
 		return fact;
 	}
-	public static Long factorial(Long num){
+	public static Long factorial(Long num) throws InvalidParameterException{
 		Long fact = 1L;	//The value of the factorial
 
+		//If the number passed in is < 0 throw an exception
+		if(num < 0){
+			throw new InvalidParameterException("n! cannot be negative");
+		}
 		//Loop through every number up to and including num and add the product to the factorial
 		for(Long cnt = 2L;cnt.compareTo(num) <= 0;++cnt){
 			fact *= cnt;
@@ -647,9 +655,13 @@ public class Algorithms{
 
 		return fact;
 	}
-	public static BigInteger factorial(BigInteger num){
+	public static BigInteger factorial(BigInteger num) throws InvalidParameterException{
 		BigInteger fact = BigInteger.valueOf(1L);
 
+		//If the number passed in is < 0 throw an exception
+		if(num.compareTo(BigInteger.ZERO) < 0){
+			throw new InvalidParameterException("n! cannot be negative");
+		}
 		//Loop through every number up to and including num and add the product to the factorial
 		for(BigInteger cnt = BigInteger.TWO;cnt.compareTo(num) <= 0;cnt = cnt.add(BigInteger.ONE)){
 			fact = fact.multiply(cnt);