what is thread safe in java?

[saravanan]

when i read java articales or books i often read thread safe in servlets. what is the meaning for thread safe give me a example program for thread safe?

[amansundar]

In computer programming, thread-safe describes a program portion or routine that can be called from multiple programming threads without unwanted interaction between the threads. (A thread is an instance of the program running on behalf of some user or process.) Thread safety is of particular importance to Java programmers, since Java is a programming language that provides built-in support for threads. By using thread-safe routines, the risk that one thread will interfere and modify data elements of another thread is eliminated by circumventing potential data race situations with coordinated access to shared data.

It is possible to ensure that a routine is thread-safe by:

1. Making sure that concurrent threads use synchronized algorithms that cooperate with each other.
2. Confining the address of a shared object to one thread whenever an unsynchronized algorithm is active..