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Is there an approach to finding the ASCII distance between two strings of 5 characters

I am trying to find a way to calculate and print the Ascii distance between a string from user input
Scanner scan = new Scanner(System.in);
System.out.print("Please enter a string of 5 uppercase characters:");
String userString = scan.nextLine();
and a randomly generated string
int leftLimit = 65; // Upper-case 'A'
int rightLimit = 90; // Upper-case 'Z'
int stringLength = 5;
Random random = new Random();
String randString = random.ints(leftLimit, rightLimit + 1)
.filter(i -> (i <= 57 || i >= 65) && (i <= 90 || i >= 97))
.limit(stringLength)
.collect(StringBuilder::new, StringBuilder::appendCodePoint, StringBuilder::append)
.toString();
Is there a way to calculate the distance without having to separate each individual character from the two strings, comparing them and adding them back together?

Use Edit distance (Levenshtein distance)
You can
Implement your own edit distance based on the algorithm on wikipedia,
you can use an existing source code, for that look at rosetta code.
use an existing library like apache LevenshteinDistance
you can also check
Levenshtein Distance on stackoverflow

Streams are, well, as the name says, streams. They don't work very well unless you can define an operation strictly on the basis of one input: One element from a stream, without knowing its index or referring to the entire collection.
Here, that is a problem; after all, to operate on, say, the 'H' in your input, you need the matching character from your random code.
I'm not sure why you find 'separate each individual character, compare them, and add them back together' is so distasteful to you. Isn't that a pretty clean mapping from the problem description to instructions for your computer to run?
The alternative is more convoluted: You could attempt to create a mixed object that contains both the letter as well as its index, stream over this, and use the index to look up the character in the second string. Alternatively, you could attempt to create a mix object containing both characters (so, for inputs ABCDE and HELLO, an object containing both A and H), but you'd be writing far more code to get that set up, then the simple, no-streams way.
So, let's start with the simple way:
int difference = 0;
for (int i = 0; i < stringLength; i++) {
char a = inString.charAt(i);
char b = randomString.charAt(i);
difference += difference(a, b);
}
You'd have to write the difference method yourself - but it'd be a very very simple one-liner.
Trying to take two collections of some sort, and from them create a single stream where each element in the stream is matching elements from each collection (so, a stream of ["HA", "EB", "LC", "LD", "OE"]) is generally called 'zipping' (no relation to the popular file compression algorithm and product), and java doesn't really support it (yet?). There are some third party libraries that can do it, but given that the above is so simple I don't think zipping is what you're looking for here.
If you absolutely must, I guess i'd look something like:
// a stream of 0,1,2,3,4
IntStream.range(0, stringLength)
// map 0 to "HA", 1 to "EB", etcetera
.mapToObj(idx -> "" + inString.charAt(idx) + randomString.charAt(idx))
// map "HA" to the difference score
.mapToInt(x -> difference(x))
// and sum it.
.sum();
public int difference(String a) {
// exercise for the reader
}

Create an 2D array fill the array with distances - you can index directly into the 2D array to pull out the distance between the characters.
So one expression that sums up a set of array accesses.

Here is my code for this (ASCII distance) in MATLAB
function z = asciidistance(input0)
if nargin ~= 1
error('please enter a string');
end
size0 = size(input0);
if size0(1) ~= 1
error ('please enter a string');
end
length0 = size0(2);
rng('shuffle');
a = 32;
b = 127;
string0 = (b-a).*rand(length0,1) + a;
x = char(floor(string0));
z = (input0 - x);
ascii0 = sum(abs(z),'all');
ascii1 = abs(sum(z,'all'));
disp(ascii0);
disp(ascii1);
disp(ascii0/ascii1/length0);
end
This script also differentiates between the absolute ASCII distance on a per-character basis vs that on a per-string basis, thus resulting in two integers returned for the ASCII distance.
I have also included the limit of these two values, the value of which approaches the inverse of the length of strings being compared. This actually approximates the entropy, E, of every random string generation event when run.
After standard error checking, the script first finds the length of the input string. The rnd function seeds the random number generator. the a and b variables define the ASCII table minus non-printable characters, which ends at 126, inclusively. 127 is actually used as an upper bound so that the next line of code can generate a random string of variables of input length. The following line of code turns the string into the alphanumeric characters provided by the ASCII table. The following line of code subtracts the two strings element-wise and stores the result. The next two lines of code sum up the ASCII distances in the two ways mentioned in the first paragraph. Finally, the values are printed out, as well as providing the entropy, E, of the random string generation event.

Java Hexadecimal to Decimal conversion: Custom Logic

I am trying to figure out how to convert hex into a string and integer so I can manipulate an RGB light on my arduino micro-controller through it's serialport. I found a good example on the java website, but I'm having a difficult time understanding some of the methods and I am getting hung up. I could easily just copy-paste this code and have it work but I want to fully understand it. I will add comments to my understandings and hopefully someone can provide some feedback.
public class HexToDecimalExample3{
public static int getDecimal(String hex){ //this is the function which we will call later and they are declaring string hex here. Can we declare string hex inside the scope..?
String digits = "0123456789ABCDEF"; //declaring string "digits" with all possible inputs in linear order for later indexing
hex = hex.toUpperCase(); //converting string to uppercase, just "in case"
int val = 0; //declaring int val. I don't get this part.
for (int i = 0; i < hex.length(); i++) //hex.length is how long the string is I think, so we don't finish the loop until all letters in string is done. pls validate this
{
char c = hex.charAt(i); //char is completely new to me. Are we taking the characters from the string 'hex' and making an indexed array of a sort? It seems similar to indexOf but non-linear? help me understand this..
int d = digits.indexOf(c); //indexing linearly where 0=1 and A=11 and storing to an integer variable
val = 16*val + d; //How do we multiply 16(bits) by val=0 to get a converted value? I do not get this..
}
return val;
}
public static void main(String args[]){
System.out.println("Decimal of a is: "+getDecimal("a")); //printing the conversions out.
System.out.println("Decimal of f is: "+getDecimal("f"));
System.out.println("Decimal of 121 is: "+getDecimal("121"));
}}
To summerize the comments, it's primarily the char c = hex.charAt(i); AND the val = 16*val + d; parts I don't understand.

Ok, let's go line for line
public static int getDecimal(String hex)
hex is the parameter, it needs to be declared there, so you can pass a String when you call the function.
String digits = "0123456789ABCDEF";
Yes, this declares a string with all characters which can occur in a hexadecimal number.
hex = hex.toUpperCase();
It converts the letters in the hex-String to upper case, so that it is consistent, i.e. you always have F and never f, no matter which is being input.
int val = 0;
This is the variable where the corresponding decimal value will later be in. We will do our calculations with this variable.
for (int i = 0; i < hex.length(); i++)
hex.length() is the number of characters in the hex-String provided. We execute the code inside this for loop once per character.
char c = hex.charAt(i);
Yes, char represents a single character. We retrieve the character from the hex-String at index i, so in the first iteration it is the first character, in the second iteration the second character and so on.
int d = digits.indexOf(c);
We look which index the character has in the digit-String. In that way we determine the decimal representation of this specific digit. Like 0-9 stay 0-9 and F becomes a 15.
val = 16*val + d;
Let's think about what we have to do. We have the decimal value of the digit. But in hexadecimal we have this digit at a specific position with which it gets multiplied. Like the '1' in '100' is actually not a 1, but 100 * 1 because it is at this position.
10 in hexadecimal is 16 in decimal, because we have 1 * 16. Now the approach here is a little bit complicated. val is not uninitialized. val is 0 at the beginning and then contains the cumulated values from the previous iterations. Since the first character in the String is the highest position we don't know directly with what we have to multiply, because we don't know how many digits the number has (actually we do, but this approach doesn't use this). So we just add the digit value to it. In the consecutive iterations it will get multiplied by 16 to scale it up to the corresponding digit base value. Let me show you an example:
Take 25F as hex number. Now the first iteration takes the 2 and converts it to a 2 and adds it to val. The 16 * val resolves to 0 so is not effective in the first time.
The next iteration multiplies the 2 with 16 and takes the 5 (converted to 5) and adds it to val. So now we have (I split it mathematically so you understand it):
2 * 16 + 5
Next we get the F which is decimal 15. We multiply val by 16 and add the 15.
We get 2 * 256 + 5 * 16 + 16 (* 1), which is actually how you calculate the decimal value of this hex value mathematically.
Another possibility to compute val is:
val += Math.pow(16, hex.length() - i - 1) * d;

String Contatenation with primitives in java

I just recently started learning Basics in Java, and was testing around initializing a string variable by concatenating primitive variables.
public class Main{
public static void main(String[] args){
byte lbyte = 3;
short lshort = 1;
int lint = 1;
long llong = 0;
float lfloat = 2.0f;
double ldouble = lfloat;
char lchar = 'H';
boolean lbool = true;
String lstring = " w0r1d ";
String lOutput = lchar+lbyte+lshort+lint+llong+lstring+ldouble+' '+lbool;
System.out.println(lOutput);
}
}
In this code, my objective was to create a string that would output:
H3110 w0r1d 2.0 true
However, when i run it the output is: 77 w0r1d 2.0 true
The unexpected result is the 77, while the rest is fine. Even if i would assume the number variables would get added, it would only be a total of 5. The variable lchar is also apparently "absorbed" into the numbers.
Where did the 77 come from and what happened to the H in lchar?
Edit: the goal is to use as much primitive variables as possible in the concatenation.
Edit2: Thanks for all the helpful answers.

The ASCII / Unicode value for 'H' is 72. The additions are processed left to right, so lchar + lbyte is 'H' + (byte) 3 which is equal to 72 + 3.
You'll only get a string result from + if one of the operands is a string. That doesn't happen until you finally concatenate lstring, which explains why all of the numerical (and the char) variables are added together to get 77. Everything to the right of lstring is concatenated one by one, each converted to a string, since the left hand operands of all those +s are all strings at that point.
A quick fix is to start with "" to force everything to be done with strings.
String lOutput = ""+lchar+lbyte+lshort+lint+llong+lstring+ldouble+' '+lbool;

The 77 came from when you were adding the chars. When adding chars it adds their values since they act like integers. Also the other variables which are numbers might have added together. 'H' = 72 in java and 72 + 3 = 75 and 75 + 1 = 76 and finally 76 + 1 = 77.
To fix this you can put "" at the beginning of where you are building your string.
Fix:
String lOutput = ""+lchar+lbyte+lshort+lint+llong+lstring+ldouble+' '+lbool;

Java evaluates expressions like that left to right so what's happening is that you're telling Java to add a char and a byte together and Java will then take the integer value of the character (72) and add the integer value of the byte (3) to it.
So what you're really telling Java is to do this:
String lOutput = (72+3+1+1+0)+" w0r1d"+2.0+' '+true;
When Java comes to +" w0r1d" it will convert the first part into a String and concatenate them, but before that you're adding types where + is defined as addition and therefore Java will sum them up to 77.
To get the desired behaviour you need to start out with a String, so doing this will work as you want it to:
String lOutput = String.valueOf(lchar)+lbyte+lshort+lint+llong+lstring+ldouble+' '+lbool;

This is for automatic type conversion.Look the in the ASCI chart the integer representation of capital 'H' is 72. At first the 'H' is upgraded to int from char and then it is concatenated with the string right to it

Can I multiply charAt in Java?

When I try to multiply charAt I received "big" number:
String s = "25999993654";
System.out.println(s.charAt(0)+s.charAt(1));
Result : 103
But when I want to receive only one number it's OK .
On the JAVA documentation:
the character at the specified index of this string. The first character is at index 0.
So I need explanation or solution (I think that I should convert string to int , but it seems to me that is unnesessary work)

char is an integral type. The value of s.charAt(0) in your example is the char version of the number 50 (the character code for '2'). s.charAt(1) is (char)53. When you use + on them, they're converted to ints, and you end up with 103 (not 100).
If you're trying to use the numbers 2 and 5, yes, you'll have to parse them. Or if you know they're standard ASCII-style digits (character codes 48 through 57, inclusive), you can just subtract 48 from them (as 48 is the character code for '0'). Or better yet, as Peter Lawrey points out elsewhere, use Character.getNumericValue, which handles a broader range of characters.

Yes - you should parse extracted digit or use ASCII chart feature and substract 48:
public final class Test {
public static void main(String[] a) {
String s = "25999993654";
System.out.println(intAt(s, 0) + intAt(s, 1));
}
public static int intAt(String s, int index) {
return Integer.parseInt(""+s.charAt(index));
//or
//return (int) s.charAt(index) - 48;
}
}

Alphabet constant in Java?

I have a situation where I need to find a letter's index in the alphabet. In Python I could use string.ascii_lowercase or string.ascii_uppercase. Is there something similar in Java?
Obviously I could do:
private static char[] alphabet = "abcdefghijklmnopqrstuvwxyz".toCharArray();
But after so much Python, it makes me wonder if this is built in somewhere.

You can get the index like this:
char lowercaseLetter = ...
int index = lowercaseLetter - 'a';

Although I would prefer ColinD's approach whenever it fits I just want to mention that Java actually has some sort of API for this. It allows you to parse numbers with a radix of up to 36 which use the 10 digits from '0'-'9' and the letters 'a'-'z' for the rest of the range (in either case).
char letter = ...
int index = Character.digit( letter, 36 ) - 10;
and back
int index = ...
char ch = Character.forDigit( index + 10, 36 );
In case you actually want to use this to create or parse radix 36 numbers, you can use the Integer.parseInt and Integer.toString static method implementations that take a radix parameter.