I need to convert the rest of the division by 16 to Hexadecimal. I'm using the Integer.toHexString method and pass the value (variable "resto") that I need to convert to hexadecimal, but the ouput ... More on stackoverflow.com

Hello everyone, I've just started with Java recently, and i'm just trying to code some in Java. I came up with this idea for an app to convert decimal -> hexadecimal, decimal -> binary and vice... More on forums.oracle.com

Well, you are still converting it to integer at some point if you are using division, but once you've converted it to a binary string it would be easy to go from binary to hex, as every 4 bits is 1 hex digit. If you are coverting the input string to int you just keep using % 16 and / 16 until it's 0 More on reddit.com

Let's walk through all of it. I hate the variable names in this method. I'm going to rewrite it like a person who has some sense: static string ToHexadecimal(int input) { if (input <= 0) { return String.Empty; } var head = ToHexadecimal(input / 16); var remainder = input % 16; var tail = (char)(remainder + (remainder >= 10 ? 'A' - 10 : '0')); return head + tail; } Rewriting some helper methods would make it more clear later, but let's do it line by line, then we'll focus on the tough parts. static string ToHexadecimal(int input) I chose the names because this is a function that takes an int and converts it to a string in hexadecimal format. DECtoHEX is a poor name because an int isn't in any format whatsoever. It's a number. Generally conversion methods are expected to read like "parameter to something". I also like naming my inputs input. That's more clear than DEC1, which implied there's a DEC2 somewhere, or perhaps "December first". It's hard to get anything done when we don't use names that make sense. Now the method is "integer ToHexadecimal string", not "DEC1 DECtoHEX string". Nice. if (input <= 0) { return String.Empty; } Recursive methods have to have a "base" case, the one where they don't recurse. This method will return an empty string if the input is less than or equal to 0, so when thinking about the loop, we'll think about when this is true. var head = ToHexadecimal(input / 16); Here is our loop. It's going to keep the result of calling itself on some other number in a variable named head. I'm guessing from the name this part is intended to be the front of a string. This makes sense. Usually recursive string algorithms involve methods that return one character at a time. And if you think about it, this call will eventually hit the base case. It's integer division, so it rounds. If we call ToHexadecimal(17), it will get here and call ToHexadecimal(17 / 16). Since we're doing integer division, 17 / 16 == 1. That will end up getting to this line again and call ToHexadecimal(1 / 16), which is 0. We saw above that returns "". But we don't know what the other calls return until we keep going. var remainder = input % 16; The % operator is "mod", and finds the remainder of division. So 17 % 16 == 1, 18 % 16 = 2, etc. We don't see how it's used yet, but at least it's straightforward. var tail = (char)(remainder + (remainder >= 10 ? 'A' - 10 : '0')); Don't write lines like this ever. It does way too much on one line. In order to explain this to you I want to take it in chunks. First: do you know what the ternary operator does? IT's the ? : part in the line above. The best way to explain it is to say that this line: int result = IfSomething() ? 100 : 900; Is the same as this code: bool result; if (IsSomething) { result = 100; } else { result = 900; } It's a shortcut for that, but can be used to cram too many things onto one line often. Which is what's going on here. At the far right, we see: (remainder >= 10 ? 'A' - 10 : '0') We could rewrite this: char result; if (remainder >= 10) { result = 'A' - 10; } else { result = '0'; } That might still be a little confusing to you. To understand it, you need to know some assumptions it makes and some dirty details of the char type. To try and keep it short, everything in a computer is a number. A string like "dog" is really 3 numbers. The rules that dictate how numbers correspond to symbols are called "encodings". Long story short: the digits 0 through 9 happen to be right next to the letter 'A' in the encodings we tend to use. Because of that, in a lot of languages the type char is synonymous with numbers, and lots of weird tricks work. So C# here is letting you do something that looks goofy until you know all of that. What's going on here gets even weirder. So let's just go ahead and say what this does and know we'll need it later: "It returns a char. If the remainder is >= 10, that char is whatever is 10 before the letter 'A'. If not, that char is 0. That makes the next bit a little easier: (char)(remainder + ) Aha. Now that we see the whole thing, it starts to make sense. We know that the above is either going to give us '0' or 'A' - 10. So let's walk through some results here. If our remainder is 0-9, we're going to get that number. So let's say remainder is 7. We'll get '0' out of the last part, and our line becomes: (char)(7 + '0') It just so happens the digits are laid out in ASCII next to each other in most encodings. So if you add 7 to the number that means '0', you get '7'. This is a way to turn an int from 0-9 into the char that represents it! Now let's say our remainder is 12. We'll have A - 10 and end up with: (char)(12 + ('A' - 10)) We can rearrange this and see it could actually mean: (char)('A' + 2) And there we go. The letter 2 spaces after 'A' is C, which happens to be how we represent hexadecimal 12. So this line is a silly tricky way for "figure out which character should represent the remainder". Here's how we'd write it if we wanted other people to have half a chance of understanding us: private char GetCharFor(int remainder) { var offset = (remainder >= 10) ? 'A' - 10 : '0'; return (char)(remainder + offset); } That changes the last two lines to: var tail = GetCharFor(remainder); return head + tail; Ah, now it makes more sense. Walk through the calls on paper: ToHexadecimal(135) = "87" head = ToHexadecimal(8) == "8" head = ToHexadecimal(0) == "" remainder = 8 % 16 = 8 return "" + '8' remainder = 135 % 16 = 7 tail = '7' return "8" + '7' See how it works now? More on reddit.com