how to declare string?

Answer 1

exist also: StringBuilder and StringBuffer "Multithread"

Answer 2

There are two ways to do this by String literal and by new. String literal is preferred way due to better performance and low memory consumption.

string literal:
String name = "Piyush"

String class:
String name = new String ("piyush");

Answer 3

String greeting = "Hi how are you";

Answer 4

String x="hello "