非抽象类的抽象方法线程安全

Question

I have an abstract class with non abstract methods. I want to know if these non abstract methods are thread safe by default?

To make the question more clear, here is an example

public abstract Class Animal {
  private List foo;
  non abstract method survive() {
    //bla bla bla
    foo++;
    foo = foo * 2
    foo = nul
    //bla bla bla
  }  
  abstract method eat();
  abstract method sleep();
}

public class Cat extends Animal {
  eat();
  sleep();
}

public class Dog extends Animal {
  eat();
  sleep();
}

//etc etc

If both the Cat and Dog wants to survive at the same time, does Java takes care of it by default? Or should I make the Animal.survive() method as synchronized?

Answer 1

Abstract class methods are not any special in terms of concurrent access. If you are working on a static resource in your non-abstract method then you should make it synchronize to avoid any concurrent access problem.

Answer 2

If class A extends class B, then all the objects of class B can use public and non-abstract methods from A. Obviously, you can override this functions in B, but if you won't do this, then there would be no problem in using (public, non-abstract) functions from A.

Word abstract in A put in front of a method means, that you have to override it in the subclass.

Answer 3

好吧，根本没有问题，因为Dog和Cat是独立的对象->没有同步问题...

Answer 4

"Writing thread safe code is, at its core, about managing access to state, and in particular to shared, mutable state." - Java Concurrency In Practice -

foo state is very important.