Hexadecimal to Decimal Converter()

Step 1: Understand Hexadecimal to Decimal Conversion

In order to convert a hexadecimal string into decimal in Java, we first need to understand that a hexadecimal number is a number in base 16 while decimal is a number in base 10. Each digit in a hexadecimal number represents a power of 16. For example, '1A' would be 26 in decimal (116^1 + 1016^0).

Step 2: Parsing the Hexadecimal String

Java provides a built-in method for converting a hexadecimal string into a number. This method is Integer.parseInt(). It takes two arguments. The first is the string that we want to convert and the second is the base of the number system of the string, which is 16 in this case.

String hexStr = "1A";
int num = Integer.parseInt(hexStr, 16);
System.out.println(num);

The above code will print out '26', which is the decimal equivalent of the hexadecimal number '1A'.

Step 3: Writing the Conversion Function

Now, let's encapsulate this functionality into a function that we can use to convert any hexadecimal string into a number. This function takes a string as input and returns the integer equivalent of the hexadecimal string.

public static int hexToDecimal(String hexStr) {
    return Integer.parseInt(hexStr, 16);
}

Step 4: Handling Exceptions

There is a possibility that the input string is not a valid hexadecimal number. For example, it might contain characters other than 0-9 and A-F. To handle these cases, it is necessary to add exception handling to our function.

public static int hexToDecimal(String hexStr) {
    try {
        return Integer.parseInt(hexStr, 16);
    } catch (NumberFormatException e) {
        System.out.println(hexStr + " is not a valid hexadecimal number");
        return 0;
    }
}

Step 5: Testing the Function

Finally, we can test our function by calling it with various inputs.

public static void main(String[] args) {
    System.out.println(hexToDecimal("1A"));  // 26
    System.out.println(hexToDecimal("FF"));  // 255
    System.out.println(hexToDecimal("ZZ"));  // Not a valid hexadecimal number
}

Conclusion

In this post, we have explained how to write a function in Java to convert a hexadecimal number to its decimal equivalent. The function uses Java's Integer.parseInt() method to perform the conversion, with error handling for invalid hexadecimal strings.

Here's the full code:

public class Main {

    public static int hexToDecimal(String hexStr) {
        try {
            return Integer.parseInt(hexStr, 16);
        } catch (NumberFormatException e) {
            System.out.println(hexStr + " is not a valid hexadecimal number");
            return 0;
        }
    }

    public static void main(String[] args) {
        System.out.println(hexToDecimal("1A"));  // 26
        System.out.println(hexToDecimal("FF"));  // 255
        System.out.println(hexToDecimal("ZZ"));  // Not a valid hexadecimal number
    }
}