java - assignment operator String object -

i new java programming. have read in book

string a="hello"; string b="hello"; system.out.println(a==b); 

this should return false & b refer different instances of string objects.

bcoz assignments operator compares instances of objects still getting true.
using eclipse ide.

example in book goes this:

string s = "s"; string stoo = "s"; system.out.println(a == b); system.out.println(s == stoo); 

that bit of code prints “false” s == stoo. that's because s , stoo references different instances of string object. so, though have same value, not equal in eyes of equality operators. also, s == “s” prints false, because string literal produces yet instance of string class.

name of book: java 7 absolute beginners

this optimisation called string pooling in compile-time constant strings (aka known identical at compile time) can set such same object in memory (saving space 1 of used types of object). or in words of docs;

"all literal strings , string-valued constant expressions interned."

note applies strings defined @ compile time, following print false.

string a="hello"; string b=new string("hello"); system.out.println(a==b); //prints false because new string forced 

or

string a="hello"; string b1="he"; string b2="llo"; string b=b1+b2;  system.out.println(a==b); //prints false because b wasn't know "hello" @ compile time not use string pooling 

n.b. possible cause second snippet print true making b1 , b2 final, allowing b1+b2 known @ compile time. in need careful , treat string==string considerable respect, in vast majority of cases want string.equals(string) in behaviour not exist.