how many String objects created??

[vineet walia]

 public String makinStrings() {
 String s = “Fred”;
 s = s + “47”;
 s = s.substring(2, 5);
 s = s.toUpperCase();
 return s.toString();
 }

How many String objects will be created when this method is invoked?

[krishna kanthgaru]

1. Fred
2. Fred47
3. ed47
4. ED47

there must something , if a ranch hand is asking. enlighten us , vineet

vineet walia wrote:

 public String makinStrings() {
 String s = “Fred”;
 s = s + “47”;
 s = s.substring(2, 5);
 s = s.toUpperCase();
 return s.toString();
 }

How many String objects will be created when this method is invoked?

[Nitish Bangera]

Actually, if you are reading K&B SCJP6 then it can be answered at Pg434. When a string literal is encountered, the string object is created when the class is loaded. SO Fred and 47 are compile time constants and are created when the class is loaded. But at run time Fred47,ed47 and ED47 are created. s.toString doesn't create a new string as that string is already there in the string pool. Read about Compile time Constants

[Himanshu Kansal]

3. ed47

ed4 you mean

Total strings ever created during the codes lifecycle is 5. "47" is a compile time constant so does not reach run-time, where only 4 would be created.

Regards

[Nitish Bangera]

3 would be created. toString returns a String and that object is already there in the pool.

[Himanshu Kansal]

Nitish Bangera wrote:3 would be created. toString returns a String and that object is already there in the pool.

the others are created before that itself, as told by Krishna

[bhavya passion]

Five string object are created
They are: Fred,47,fred47,ed4,ED4.

[Himanshu Kansal]

bhavya passion wrote:Five string object are created
They are: Fred,47,fred47,ed4,ED4.

Yes Bhavya! But let's re-iterate Nitish's important point that "47" is resolved at compile-time. So 4 left at run-time

[Nitish Bangera]

Fred also created when the class is loaded. so it makes Fred and 47 at class loading time. SO 3 at runtime.

[Ankit Garg]

This question has been asked many times before. Please search the forum before asking a question

https://coderanch.com/t/434127/Programmer-Certification-SCJP/certification/many-String-Objects-are-created

https://coderanch.com/t/426859/Programmer-Certification-SCJP/certification/many-String-Objects-would-created

https://coderanch.com/t/426115/Programmer-Certification-SCJP/certification/StringObjects

https://coderanch.com/t/424671/Programmer-Certification-SCJP/certification/What-output-related-string

..............

[Tanmoy Dhara]

String s = "fred" will be created when the class will be loaded and the reference will be added to the string pool so that if in future any satement uses "fred",it will just refer to the existing object in stead of making a new one ( although thats not needed here)

so, 3 objects at runtime will be created.

But, i have one question, what if they do not specify runtime or compilation time???Should i write 4 or i assume they are refering to the runtime scenario??

[Nitish Bangera]

5 object will be created in all. They won't be asking runtime or compilation time.

[Himanshu Kansal]

"fred" athough resolved at compile-time, has an active reference at runtime. A class compiled today might be run after N years. If the literal is saved today it cannot stay till N years. As soon as the scope of compilation ends, literal's life ends. The reference needs to be resolved at runtime as well. So "fred" is spawned at runtime also. Then again it depends on the string-pool.

[Tanmoy Dhara]

@ Nitish

forgot there was also "47" hope,i won't get used to overlooking things