A hexadecimal number is a number represented in the base-16 number system, which uses digits 0–9 and letters A–F to represent values from 0 to 15. The decimal number system is a base-10 number system that uses digits 0–9.
- Each hexadecimal digit is processed from left to right.
- The method also handles lowercase hexadecimal letters such as a–f.
Illustration:
Input : 1AB
Output: 427
Input : 1A
Output: 26
Approach to Convert Hexadecimal to Decimal
To convert hexadecimal to decimal:
- Start from the rightmost hexadecimal digit.
- Convert each digit or letter into its decimal value.
- Multiply the value by the corresponding power of 16.
- Add all the values to get the decimal number.
- Repeat until all hexadecimal digits are processed.
Example:Program to Convert Hexadecimal to Decimal
class GFG {
static int hexadecimalToDecimal(String hex) {
int decimal = 0;
for (int i = 0; i < hex.length(); i++) {
char ch = Character.toUpperCase(hex.charAt(i));
int value;
if (ch >= '0' && ch <= '9') {
value = ch - '0';
} else if (ch >= 'A' && ch <= 'F') {
value = ch - 'A' + 10;
} else {
throw new IllegalArgumentException("Invalid hexadecimal number");
}
decimal = decimal * 16 + value;
}
return decimal;
}
public static void main(String[] args) {
String hex = "1AB";
int decimal = hexadecimalToDecimal(hex);
System.out.println("Decimal equivalent of " + hex + " is: " + decimal);
}
}
Output
Decimal equivalent of 1AB is: 427
Explanation: The hexadecimalToDecimal() method processes each hexadecimal digit from left to right. Numeric characters are converted directly, while A–F are converted to values 10–15. The decimal result is updated using decimal = decimal * 16 + value. For 1AB, the calculation becomes ((1 × 16) + 10) × 16 + 11 = 427.
