Why are curly brackets used in java..??

Answer 1

Curly brackets are used in many programming languages for block of code
For example
int main ()
{
Cout<<"you have to understand man"";
}
This is to contain the code in the main function that is the int main

Answer 2

for scoping.
in other words: to show you in what code block you are working.
a statement followed by { says: “hey, everything following the { goes with me and only ends when I see }