how am i able to change value of same String?

Question

i know Strings are immutable in java and i just read some theory about it Once a String is declared it cannot be changed . i declared a String and changed it's value just by appending some value to it . it should not have happened

   String s = "amol";
   s = s + "abc";
   System.out.println(s); //output is amolabc

You didn't change the `String`. You created a new one and assigned it to the same variable. — bradimus, Feb 19 '16 at 04:35
you need to learn string pool and how to store string value in string pool. you will get answer. — Piyush Gupta, Feb 19 '16 at 04:39
@Amol you can also work with the String object to stich strings and make char arrays strings and things like that. — Ashwin Gupta, Feb 19 '16 at 04:42
Note that you can still break immutability of String using *reflection* — TheLostMind, Feb 19 '16 at 04:55

score 1 · Answer 1 · answered Feb 19 '16 at 04:37

1

The String s didn't get changed. When you did s + "abc", it created a new String object with the result of the operation.

answered Feb 19 '16 at 04:37

MujjinGun

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score 0 · Answer 2 · answered Feb 19 '16 at 04:39

0

You need to understand the concept of String Pool in Java. Please go through the link http://www.javaranch.com/journal/200409/ScjpTipLine-StringsLiterally.html

answered Feb 19 '16 at 04:39

Ramachandra Reddy

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score 0 · Answer 3 · answered Feb 19 '16 at 04:40

You are right that Strings are immutable. Here, You didn't change the String s. All distinct Strings are stored in the Heap Memory. So, all the variables (say 10 variables ) containing the same String (say "Hello" ) will occupy only 5 bytes of memory. They all will point to the same location. Separate instances will not be stored for each of those variables. Here, when you write s = s + "abc", a new string "amolabc" is created in the heap,and now the variable s just points to the new string in the heap. You didn't modify the value of "amol". You just made a new String.

score 0 · Answer 4 · answered Feb 19 '16 at 04:40

The meaning of immutable is not like you thought to be.Being immutable guarantees that hashcode will always the same, so that it can be cashed without worrying the changes.That means, there is no need to calculate hashcode every time it is used.

here you are appending another string value to it,which can be done.But you cannot concatenate with another string.

By appending it is creating another string.

Refer here

how am i able to change value of same String?

4 Answers4