How java handles string literals

Question

in java, I created 2 string literals with the same value

String a = "Hello";
String b = "Hello";

now both of them should have the same link

System.out.println(a==n); // returns true

but when i do

b+=" World";
System.out.println(a==b); // returns false

Now I have 2 questions

1. Why a and b do not refer to the same object after the operation "b + ="? 2. How can I change line b without error? (Because I read the String class unchanged)

Answer 1

The reason you can change bis because you technically create a new String object and assign it to an existing link.

b += " World"

coincides with

b = b + " World";

b String. , , a b , b , , a "Hello World", a==b .

String StringBuffer StringBuilder. .append() .

Answer 2

• b+=" World", , , .

• , b. final, .

Answer 3

• a b String. b , .

• , "" , . .