JavaAlgorithms/Conversions/DecimalToAnyBase.java

package Conversions;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.ArrayList;

/** @author Varun Upadhyay (https://github.com/varunu28) */

// Driver Program
public class DecimalToAnyBase {
  public static void main(String[] args) throws Exception {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    System.out.println("Enter the decimal input below: ");
    int decInput = Integer.parseInt(br.readLine());
    System.out.println();

    System.out.println("Enter the base below: ");
    int base = Integer.parseInt(br.readLine());
    System.out.println();

    System.out.println("Decimal Input" + " is: " + decInput);
    System.out.println(
        "Value of " + decInput + " in base " + base + " is: " + convertToAnyBase(decInput, base));

    br.close();
  }

  /**
   * This method produces a String value of any given input decimal in any base
   *
   * @param inp Decimal of which we need the value in base in String format
   * @return string format of the converted value in the given base
   */
  public static String convertToAnyBase(int inp, int base) {
    ArrayList<Character> charArr = new ArrayList<>();

    while (inp > 0) {
      charArr.add(reVal(inp % base));
      inp /= base;
    }

    StringBuilder str = new StringBuilder(charArr.size());

    for (Character ch : charArr) {
      str.append(ch);
    }

    return str.reverse().toString();
  }

  /**
   * This method produces character value of the input integer and returns it
   *
   * @param num integer of which we need the character value of
   * @return character value of input integer
   */
  public static char reVal(int num) {
    if (num >= 0 && num <= 9) return (char) (num + '0');
    else return (char) (num - 10 + 'A');
  }
}