After setting i to 1 circle of loop finished and next line of code that will be executed is i++. So, yes, in begining of next circle of loop i will be equal to 2

What exactly does setting i to 1 in the for loop do? I can see that it matters, because you lose multiples of 2 if you take it out, but I don't understand what it does. When the conditions of the for loop are evaluated once i is set to 1, does i get reset to 2?

thank you!

no.

Is recursion faster/uses less memory than a for loop?

When I put this into eclipse like it is, then try some examples in the main method, I get the following error messages:
For example:
public static void main(String[] args) {
System.out.println(camelCase("thisIsOneString"));
}

Exception in thread "main" java.lang.IndexOutOfBoundsException: No group 1
at java.base/java.util.regex.Matcher.start(Matcher.java:482)
at java.base/java.util.regex.Matcher.appendExpandedReplacement(Matcher.java:1090)
at java.base/java.util.regex.Matcher.appendReplacement(Matcher.java:997)
at java.base/java.util.regex.Matcher.replaceAll(Matcher.java:1181)
at java.base/java.lang.String.replaceAll(String.java:2142)
at DigPow/myPackage.Solution2.camelCase(Solution2.java:6)
at DigPow/myPackage.Solution2.main(Solution2.java:9)

What does it mean by group 1?