Is a class without fields thread safe

Question

If I make a class with only methods and no variables, with each method having its own local variable then, will that class be thread-safe? for eg.

   public class Client {

                public String xyz(final String inputXML) {
                      DataInputStream dis = null;
                      DataOutputStream dout = null;
                      Socket clientSocket = null;
                        //do some processing 
                    }

                public String abc(final String inputXML) {
                      DataInputStream dis = null;
                      DataOutputStream dout = null;
                      Socket clientSocket = null;
                        //do some processing 
                    }
        }

now if I launch multiple threads of this Client then, will the class be thread safe ?

It is thread safe, but if you try to open the same socket from multiple threads you will still get concurrency issues. — Adriaan Koster, Feb 12 '16 at 11:06
It is not the same Socket because there is no share data between different calls to those methods. If a new Socket is created in each thread it works on a different port on the client side so no data is mixed between socket connections. A socket is identified by the ip, port of the server and ip, port of the client. The port of the client changes in this case — Davide Lorenzo MARINO, Feb 12 '16 at 11:17

score 5 · Accepted Answer · answered Feb 12 '16 at 11:00

Yes your class is thread safe.

A method is thread safe if:

has no access to shared variables
Access to shared immutable variables
Access to variables which state can be modified only in a thread safe manner (for example via synchronized methods)
Access to variables with a synchronized block using the same lock of other threads that use the same variable

Your methods haven't access to shared variables so are thread safe

score 0 · Answer 2 · answered Feb 12 '16 at 10:59

0

Theoretically yes, practically it depends on the values of your variables if they are independent instances or if they point to the same instances somewhere in the system

answered Feb 12 '16 at 10:59

Thorsten Schiffer

190
6

Is a class without fields thread safe

2 Answers2