Why is the output not [HeLLo,Hello,HeLLo]

[Clemonte Johnstone]

Please can someone kindly explain why the output is not [HeLLo,Hello,HeLLo].

import java.util.ArrayList;
import java.util.List;

/* Consider below code:
* What will be the result of compiling and executing Test class?
* A) [HeLLo, Hello, Hello]
* B) [Hello, Hello, Hello]                CORRECT ANSWER
* C) [HeLLo, HeLLo, HeLLo]
* D) [HeLLo, Hello, HeLLo]             WRONG ANSWER
*/



public class _27_Question_Manipulating_ArrayList {
   public static void main(String[] args) {
       String s = new String("Hello");
       List<String> list = new ArrayList<>();
       list.add(s);                                            // obj ref 1
       list.add(new String("Hello"));                  // obj ref 2
       list.add(s);                                            // obj ref 1
       s.replace("l", "L");

       System.out.println(list);
   }
}

Thanks for any help that you can give.

[Dave Tolls]

What do you think the replace method call does?
The documentation might help you:
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#replace(char,char)

[Clemonte Johnstone]

Its more complicated than that, or I would not have asked. Does anyone have the patience please to explain why the two different String objects are not modified using the replace method please?

[Liutauras Vilda]

Mark Raphael Qt wrote:

Dave Tolls wrote:What do you think the replace method call does?
The documentation might help you:
https://docs.oracle.com/en/java/javase/11/docs/api/java.base/java/lang/String.html#replace(char,char)

Its more complicated than that, or I would not have asked. Does anyone have the patience please to explain why the two different String objects are not modified using the replace method please?

Did you take time to read what Dave Tolls showed you? I think you should be able to assemble the reasoning.

Some hints:
1. Strings are immutable
2. Return result not being stored anywhere

One could argue they are answers actually.

[Clemonte Johnstone]

Yes, of course it is. Thank you for the reminder I had forgotten. Also you are right, the result is not stored anywhere. Thanks again.

[Dave Tolls]

I do notice the link didn't work too well, as it seems to have dropped off the last bracket when you click on it...consequently it doesn't go to the method directly.

Also note I linked to the char version of replace and not the CharSequence version (which is the one in your code).
The reason for that is that (annoyingly) the CharSequence one does not actually talk about creating a new String and returning that new one, and the method therefore having no effect on the original String.

[Campbell Ritchie]

Dave Tolls wrote:. . . the link didn't work too well, as it seems to have dropped off the last bracket . . . .

I always use the URL button; I only have such problems if the method takes an array as a parameter. The preview button should make the problem appear. Then I have to change the [ to &lbrack; and it works. At least I think that is the trick I employ.