I've got a requirement that I have to update a MySQL table continuously and simultaneously browse the table to be used. Dirty read is appropriate. Is operation allowed in MySQL? What should i do that operation inside a Java program?

Sure, you need to simply have transactions that question the and transactions that update the DB. These may maintain different/same threads or processes. If dirty reads are acceptable, make certain your isolation level in MySQL is READ UNCOMMITTED. To know the significance of isoation levels, see:

http://en.wikipedia.org/wiki/Isolation_%28database_systems%29

To create this in MySQL:

http://dev.mysql.com/doc/refman/5.0/en/set-transaction.html