DecimalToAnyBase.java

package com.thealgorithms.conversions;

import java.util.ArrayList;
import java.util.List;

/**
 * Class that provides methods to convert a decimal number to a string representation
 * in any specified base between 2 and 36.
 *
 * @author Varun Upadhyay (<a href="https://github.com/varunu28">...</a>)
 */
public final class DecimalToAnyBase {
 private static final int MIN_BASE = 2;
 private static final int MAX_BASE = 36;
 private static final char ZERO_CHAR = '0';
 private static final char A_CHAR = 'A';
 private static final int DIGIT_OFFSET = 10;

 private DecimalToAnyBase() {
 }

 /**
 * Converts a decimal number to a string representation in the specified base.
 * For example, converting the decimal number 10 to base 2 would return "1010".
 *
 * @param decimal the decimal number to convert
 * @param base the base to convert to (must be between {@value #MIN_BASE} and {@value #MAX_BASE})
 * @return the string representation of the number in the specified base
 * @throws IllegalArgumentException if the base is out of the supported range
 */
 public static String convertToAnyBase(int decimal, int base) {
 if (base < MIN_BASE || base > MAX_BASE) {
 throw new IllegalArgumentException("Base must be between " + MIN_BASE + " and " + MAX_BASE);
 }

 if (decimal == 0) {
 return String.valueOf(ZERO_CHAR);
 }

 List<Character> digits = new ArrayList<>();
 while (decimal > 0) {
 digits.add(convertToChar(decimal % base));
 decimal /= base;
 }

 StringBuilder result = new StringBuilder(digits.size());
 for (int i = digits.size() - 1; i >= 0; i--) {
 result.append(digits.get(i));
 }

 return result.toString();
 }

 /**
 * Converts an integer value to its corresponding character in the specified base.
 * This method is used to convert values from 0 to 35 into their appropriate character representation.
 * For example, 0-9 are represented as '0'-'9', and 10-35 are represented as 'A'-'Z'.
 *
 * @param value the integer value to convert (should be less than the base value)
 * @return the character representing the value in the specified base
 */
 private static char convertToChar(int value) {
 if (value >= 0 && value <= 9) {
 return (char) (ZERO_CHAR + value);
 } else {
 return (char) (A_CHAR + value - DIGIT_OFFSET);
 }
 }
}