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Strings are immutable in java i.e. every time we make changes in string object it creates a new instance and the old object become unreferenced i.e. waste. so in a big program there will be so many unreferenced objects which can not be access. Does java manage this? how? for example- 

String s="abc";
s=s.concat("def");

now object "abc" can not be referenced at all but as strings are immutable it will still exist in the memory pool.

SpringLearner
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vivek
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  • `Does java manage this?` - of course. `how?` - we don't need to know the details, but the garbage collector looks after it. – camickr Oct 24 '13 at 05:34
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    That's the purpose and job of the Garbage Collector. You should not focus on this unless it really presents memory problems. If you run memory issues, it would be better to profile the application to detect the culprits of the memory consumption. – Luiggi Mendoza Oct 24 '13 at 05:34
  • Possible duplicate of http://stackoverflow.com/questions/2486191/java-string-pool and http://stackoverflow.com/questions/8998717/how-does-java-handle-string-objects-in-memory/8998814#8998814 – BahmanM Oct 24 '13 at 05:43

3 Answers3

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First of all, it sounds like you need a crash source in Java and garbage collection. With that said, there's a few basic points to clear up:

1) Just because an object is immutable does not mean its memory is leaked. If no references exist to an immutable object, it is just as eligible for garbage collection as any other objects.

2) String constants are an exception to this because they are always interned by the JVM. This means that string constants are kept in a special memory pool, and any time a string is created, this pool is first checked to see if that string already exists. If it does, a reference to it is returned. (You can force non-constant strings to join the pool using the String.intern() method).

3) The amount of memory these strings occupy is so minimal that you should essentially never worry about it.

Chris Hayes
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Java has automatic garbage collector which keeps running in background.This garbage collector keep checking for unused object and once it detect/find any such object it destroy it i.e. free the memory/resources used by that particular object.This is taken care by JVM so you need not worry about it.However if you want you can instruct JVM to do garbage collection .After that JVM can schedule garbage collection accordingly

To know how garbage collection works check the below link:

http://javarevisited.blogspot.in/2011/04/garbage-collection-in-java.html

http://www.oracle.com/webfolder/technetwork/tutorials/obe/java/gc01/index.html

TheGraduateGuy
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Memory management in java is done by JVM i.e Garbage Collector in JVM

All objects are stored in heap when they have reference like

MyCode ref=new MyCode();

Garbage collector validate that object for Garbage collection in two cases

  1. If reference to object becomes null
ref=null;
  1. When Island of Isolation happens

http://www.geeksforgeeks.org/island-of-isolation-in-java/

Memory management is some what different regarding String objects as above answers have already explained it

Akshay Gaikwad
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