Doubt in formal paramters

#1

how can we pass default values to formal parameters while defining a function ?

like in c++ we can do…

void fun1(int a=3){
…
…

}

#2

we cant pass default var like c++ , but you can use the Builder Pattern, as described in this Stack Overflow answer.

As described in the linked answer, the Builder Pattern lets you write code like

Student s1 = new StudentBuilder().name("Eli").buildStudent();
Student s2 = new StudentBuilder()
                 .name("Spicoli")
                 .age(16)
                 .motto("Aloha, Mr Hand")
                 .buildStudent();

in which some fields can have default values or otherwise be optional