Does this class consider ^ and $ as String and not as metacharacter.

[prachi23y]

Automaton automaton1 = RegExp("^GSA").toAutomaton();
Automaton automaton2 = new RegExp("GSA").toAutomaton();
System.out.println(automaton2.intersection(automaton1).isEmpty());

it should intersect ,but code gives me that these two patterns are unique.

[amoeller]

Please read the documentation, in particular the first item on the FAQ: https://www.brics.dk/automaton/faq.html