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Why is my String array length 3 instead of 2?

I'm trying to understand regex. I wanted to make a String[] using split to show me how many letters are in a given string expression?
import java.util.*;
import java.io.*;
public class Main {
public static String simpleSymbols(String str) {
String result = "";
String[] alpha = str.split("[\\+\\w\\+]");
int alphaLength = alpha.length;
// System.out.print(alphaLength);
String[] charCount = str.split("[a-z]");
int charCountLength = charCount.length;
System.out.println(charCountLength);
}
}
My input string is "+d+=3=+s+". I split the string to count the number of letters in string. The array length should be two but I'm getting three. Also, I'm trying to make a regex to check the pattern +b+, with b being any letter in the alphabet? Is that correct?

So, a few things pop out to me:
First, your regex looks correct. If you're ever worried about how your regex will perform, you can use https://regexr.com/ to check it out. Just put your regex on the top and enter your string in the bottom to see if it is matching correctly
Second, upon close inspection, I see you're using the split function. While it is convenient for quickly splitting strings, you need to be careful as to what you are splitting on. In this case, you're removing all of the strings that you were initially looking at, which would make it impossible to find. If you print it out, you would notice that the following shows (for an input string of +d+=3=+s+):
+
+=3=+
+
Which shows that you accidentally cut out what you were looking to find in the first place. Now, there are several ways of fixing this, depending on what your criteria is.
Now, if what you wanted was just to separate on all +s and it doesn't matter that you find only what is directly bounded by +s, then split works awesome. Just do str.split("+"), and this will return you a list of the following (for +d+=3=+s+):
d
=3=
s
However, you can see that this poses a few problems. First, it doesn't strip out the =3= that we don't want, and second, it does not truly give us values that are surrounded by a +_+ format, where the underscore represents the string/char you're looking for.
Seeing as you're using +w, you intend to find words that are surrounded by +s. However, if you're just looking to find one character, I would suggest using another like [a-z] or [a-zA-Z] to be more specific. However, if you want to find multiple alphabetical characters, your pattern is fine. You can also add a * (0 or more) or a + (1 or more) at the end of the pattern to dictate what exactly you're looking for.
I won't give you the answer outright, but I'll give you a clue as to what to move towards. Try using a pattern and a matcher to find the regex that you listed above and then if you find a match, make sure to store it somewhere :)
Also, for future reference, you should always start a function name with a lower case, at least in Java. Only constants and class names should start in a capital :)

I am trying to use split to count the number of letters in that string. The array length should be two, but I'm getting three.
The regex in the split functions is used as delimiters and will not be shown in results. In your case "str.split([a-z])" means using alphabets as delimiters to separate your input string, which makes three substrings "(+)|d|(+=3=+)|s|(+)".
If you really want to count the number of letters using "split", use 'str.split("[^a-z]")'. But I would recommend using "java.util.regex.Matcher.find()" in order to find out all letters.
Also, I'm trying to make a regex to check the pattern +b+, with b being any letter in the alphabet? Is that correct?
Similarly, check the functions in "java.util.regex.Matcher".

I have to add a string to a string for an assignment

I'm having trouble fully understanding arrays. I understand what a int array is, a set of numbers grouped together with their own locations, but I don't understand the purpose of string arrays vs strings, or how to get the user to input a string.
So, I have to make it so that the user enters a string with a % somewhere, and then another string, where the % is, the second string they enter needs to go there. I am NOT looking for a copy paste thing, but an explanation on what code I should use an what it does for that action.

You need a java.util.Scanner
You would enter a String containing a % character
Then, you String#replace that value with a second input string.
No arrays necessary...

Take first half of first string, and put it at beginning of second string based on user input

I am at the beginning chapters in my Java I class. This seems beyond what I have learned thus far.
I have to ask a user to input the first string. It could be anything. Then they have to input a second string. I have to take the first half of the first string and place it in front of the second string, then the other half of the first string and place it at the end of the first string. For example:
Enter something: ----
Enter something: word
Output: --word--
The only thing I've learned up until now is concatenation, indexes, and getting length. I have not learned arrays, if they can be relevant to this. What methods would I use to split this string up when I only know the strings after the user enters them? Even just informing me of unknown method calls would lead me in the right direction. I don't want (and can't) copy anyone's code.

Based on your example this is how you achieve that:
String firstString = "----"; //this should be read in from the user input.
String secondString = "word"; //this too should be read in from the user.
String finalString = firstString.substring(0,firstString.length()/2)+secondString+firstString.substring(firstString.length()/2,firstString.length());
Test code here
You should look into the Java StringAPI for substring. This will help you understand the code above.

You can use the substring method of the String class
something like this should work:
int idxMiddle = (string1.length()-1)/2;
string1.substring(0,idxMiddle) + string2 + string1.substr(idxMiddle);

Replacing parts of a string with characters JAVA

I know I was here earlier asking something similar, but I think I have narrowed down what i want to ask.
Ok, so I am making a program that plays the game of hangman on the jedit console. The user will guess one character at a time. At the beginning of the game, the program will display asterisks the same length of the word they are guessing. They have as many guesses as letters in the word. When they get a letter correct, the program will display the letters in place of asterisks. Here is an example of what the console should look like.
if the word is homework ********
they guess the letter e ***e**** (the bold e just happened because stars so that, it doesn't need to be bold)
then they guess the letter h h**e****
etc until there are no more asterisks
So I created a method that prints out the number of asterisks based on the number of letters in the word. I don't know how to place the letters in the place of the asterisks. I want to know if I should make a method that replaces the asterisks, or how else I can go about this. Thank you in advance for the help.
p.s I am not asking for anyone to dump code on me, that is not what I want. Just having help, and me having someone to ask questions to about things that I don't understand would be nice. by the way, I am in an intro to computer science class, so my knowledge of java is fairly low.

There are many ways you could approach this. The first that popped into my head is that you could start with a char[] the same length as the answer string. Look up the Arrays class for an easy way to fill it with asterisks. As the user guesses letters, search the answer string for that letter and replace the corresponding indexes of the char[]. Then construct a String from the char[] and display it.

Why not make something more clever, make a list of all the chars guessed so far and each time you want to print the word just go over each letter and replace it with * if not in the set.
Short: make a set of all the guesses so far. You don't have to work on the same data structure as you show the user.

I would use a list of characters instead of String for ****.
List<Character> hiddenWord = new ArrayList<Character>();
Instantiate the list with the number of * you need.
Create a function that will receive the guessed letter.
Check if the word contains that letter (use indexOf(int ch, int fromIndex) repeatedly until you get -1 - read about it here), and for each result you get that is !=-1, set the position in the array to be that letter (something like hiddenWord.set(poz, letter), where poz is the result of indexOf and letter is the guessed letter).

You can use StringBuffer insead String. In class StringBuffer exists method setCharAt.
Breifly, you will have variable String word - for guessing word, and StringBuilder guess for asterisks and guesed letters. When letter is guessed you will update guess with setCharAt.

How to make a scanner in Java that checks if the first letter is a character between A-V and if the second character is a number between 1-20?

How to make a scanner that checks if the first letter is a character between A-V and if the second character is a number between 1-20? Some examples are: '.B4', 'H10.', '**V1', 'L19*', 'M12', or 'N14'.
I'm kind a new to Java. Still learning it in school. I've followed the lessons for about half a year now.
Now I've got an assignment for school. It is about creating a text-based minesweeper. I succeeded in printing the board and placing the mines. But now I'm stuck on getting the right input.
If you use '*' in the scanner like * B4 or B4* it should mark a square.
If you use '.' in the scanner like .B4 or B4. it should unmark a square.
And if you enter B4 it should open.
But I can't get this done in a neat way. I've tried to make sub-strings of it to check if every character is the right one but after I did that my code was kind of chaotic and it didn't work as supposed to.
I've tried it like: "Example 3 : Validating vowels in: Validating input using java.util.Scanner" only I used a variable of the length of my board. So if the board was 10 by 10 it wouldn't go further than J10. But that didn't work either for me.
So I was hoping that you could help me solving this problem.

As this is an assignment, I'll just give you a guideline rather than actual code.
First, you need to get the input into some format. Consider reading the input in from the scanner and storing it into a string.
We can then make use of Java's String functions, a list of which can be found here. Try to find a function that could be useful, perhaps one that lets us get the character at a certain index.
We can then do checks on the string. First we check the first character (the character at index 0), we want to know if that is a letter from A-V. To do this we can do a check on the ASCII numbers. Assuming you just want capital letters, if we convert A to an int, then it will have the value 65. V has the value 86. All the numbers in between correspond to the ASCII values of the letters in between.
Thus we can do a check, convert the first character to an integer, let's call it x. If x >= 65 && x <= 86, then it's a letter we can care about.
Next, you need to do the number checking. For this, take a look at the function Integer.parseInt(String s). It takes a String and then converts it to an integer. You'll have to do some checks to see if it's >= 10 or <10.