package com.github.java8.lambdasinaction.chap13;
import java.util.stream.LongStream;
public class Recursion {
public static void main(String[] args) {
System.out.println(factorialIterative(5));
System.out.println(factorialRecursive(5));
System.out.println(factorialStreams(5));
System.out.println(factorialTailRecursive(5));
}
public static int factorialIterative(int n) {
int r = 1;
for (int i = 1; i <= n; i++) {
r*=i;
}
return r;
}
public static long factorialRecursive(long n) {
return n == 1 ? 1 : n*factorialRecursive(n-1);
}
public static long factorialStreams(long n){
return LongStream.rangeClosed(1, n)
.reduce(1, (long a, long b) -> a * b);
}
public static long factorialTailRecursive(long n) {
return factorialHelper(1, n);
}
public static long factorialHelper(long acc, long n) {
return n == 1 ? acc : factorialHelper(acc * n, n-1);
}
}