what is the use of the = in the regex (?=.*?[A-Z]) and why are the ? and * in front of the [a-z] because I saw in a book that they should appear behind the word or expression they should take effect on and why the two ?
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This whole RegEx
(?=.*?[A-Z])
is called a lookahead assertion, a kind of lookarounds.
It consists of three items:
(?= )
.*?
[A-Z]
The first one is the syntax for a lookahead assertion. The pattern would come in the brackets, after the initial ?=.
The second one is a dot that matches any character, with a repetition modifier *?, where the asserisk means "zero or more matches" and the question mark means "match as few as possible" instead of being greedy.
The third one I suppose you know it.
A lookaround assertion restricts the surrounding of a pattern without matching (capturing) extra things. For example:
a(?=b)
will match the letter a in ab, but not ac. Note it only matches the letter a, and the letter b is only a restriction about where the letter a should be matched. Whereas a(b) matches both letters in ab and captures the latter.
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