How should I copy Strings in Java

Question

String s    hello       String backup of s   s      s    bye     At this point  the backup variable still contains the original value  hello   this is because of String s immutability right     But is it really safe to copy Strings with this method  which is of course not safe to copy regular mutable objects   or is better to write this         String s    hello       String backup of s   new String s       s    bye     In other words  what s the difference  if any  between these two snippets     EDIT - the reason why the first snippet is safe   Let me just explain things with a little more detail  based on the good answers already provided  which were essentially focused on the question of difference of performance between the 2 snippets    Strings are immutable in Java  which means that a String object cannot be modified after its construction  Hence   String s    hello   creates a new String instance and assigns its address to s  s being a reference to the instance object   String backup of s   s  creates a new variable backup of s and initializes it so that it references the object currently referenced by s   Note  String immutability guarantees that this object will not be modified  our backup is safe  Note 2  Java garbage collection mechanism guarantees that this object will not be destroyed as long as it is referenced by at least one variable  backup of s in this case   Finally  s    bye   creates another String instance  because of immutability  it s the only way   and modifies the s variable so that it now references the new object

User · Answer

Second case is also inefficient in terms of String pool  you have to explicitly call intern   on return reference to make it intern

User · Answer

String str1  this is a string   String str2 str1 clone      How about copy like this  I think to get a new copy is better  so that the data of str1 won t be affected when str2 is reference and modified in futher action

User · Answer

Strings are immutable objects so you can copy them just coping the reference to them  because the object  referenced can t change       So you can copy as in your first example without any problem     String s    hello   String backup of s   s  s    bye

User · Answer

Since strings are immutable  both versions are safe  The latter  however  is less efficient  it creates an extra object and in some cases copies the character data    With this in mind  the first version should be preferred

User · Answer

Your second version is less efficient because it creates an extra string object when there is simply no need to do so   Immutability means that your first version behaves the way you expect and is thus the approach to be preferred

[java] How should I copy Strings in Java?

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