Answer 1

The Pattern class is used for handling regular expressions.
Regex is its own universal language and used in a wide range of situations:
- validation of text (user input), like is it a valid email or phone number
- input sanitization, defense against injection attacks
- search for substring based on complex criteria
- text parsing (processing to smaller elements based on rules)
- processing log files
And probably much more.

https://docs.oracle.com/en/java/javase/17/docs/api/java.base/java/util/regex/package-summary.html

Answer 2

Yes, but this is the kind of pattern that you mean by "butterfly pattern"?
Patterns like these are mostly used for practicing purposes. For example, you can practice loops and code logic with these patterns.

Answer 3

What pattern do you mean? A particular output? Or a design pattern? Please give an example.

Answer 4

Design patterns and regular expression patterns are different things. Do you have an example code or article i which you came across the term "pattern"? We could look it up to understand the context.

Answer 5

Do you mean something like this, for example?

"butterfly pattern"
https://simplycoding.in/butterfly-pattern-program-in-java/