Are method parameters thread safe in Java?

Question

Class Shared{    
     public void sharedMethod(Object o){
          //does something to Object
     }     
}

//this is how threads call the shared method
run(){
           


        

Answer 1

Yes, but only in two scenarios:

• if every object you pass in the o parameter is immutable,
• if your code guarantees that there is at most one thread working on the object referenced by o.

Otherwise - no, since the internal state of the object can be changed by multiple threads concurrently.