Links

http://www.tginvents.com/tushar/speedoflight.htm

http://www.tginvents.com/tushar/Ancients.htm

http://www.tginvents.com/tushar/Agasti_cell.htm

http://www.indiastar.com/kak4.htm

Few Basic Things about String intern( ) in Java

Consider a scenario when we read a csv file with very large number of records, we may end up a a lot of duplicate String objects. To avoid duplicate String objects getting created in these kind of scenarios we can use String.intern( ) method.

How it works ? Internally there will be Map/Table of String literals. First time when intern( ) is called on a String, it is added to this table. Subsequent calls String.intern ( ) will return reference to the String in the previous mentioned Table/Map.

Other benefit of interning is that == comparison is much faster.

Say you interned few Strings which got added in the previous mentioned table. How do you remove any of those from the table ? Oops ! Are we Struck here until the program ends ?

In the most recent JVMs, interned Strings are implemented as Soft references, so that they can be garbage collected soon.

Last few points:

• String literals at compile time will be automatically interned, But literals created on run time(like command line arguments) will not be interned.

Nice Talk by Jeremy Manson on Java Concurrency

No words required .. Video says it all