FunctionRecursion.java

package com.examplehub.basics;

public class FunctionRecursion {

  public static void main(String[] args) {

    /*
     * 1+2+3+...+10 = 55
     */
    System.out.println("1+2+3+...+10 = " + sum(10));

    /*
     * 1+2+3+...100 = 5050
     */
    System.out.println("1+2+3+...100 = " + sum(100));

    /*
     * 1*2*3*4*5 = 120
     */
    System.out.println("1*2*3*4*5 = " + factorial(5));

    /*
     * 1*2*3*4*5*6 = 720
     */
    System.out.println("1*2*3*4*5*6 = " + factorial(6));

    /*
     * pow(2, 3) = 8
     */
    System.out.println("pow(2, 3) = " + power(2, 3));

    /*
     * pow(2, 10) = 1024
     */
    System.out.println("pow(2, 10) = " + power(2, 10));
  }

  public static int sum(int n) {
    return n == 0 ? 0 : n + sum(n - 1);
  }

  public static int factorial(int n) {
    return n <= 1 ? 1 : n * factorial(n - 1);
  }

  public static int power(int n, int k) {
    return k == 0 ? 1 : n * power(n, k - 1);
  }
}