Local Object Reference escaping

[Neo10101]

In terms of thread safety: How can it be determined an object escapes a method call, without using JVM escape analysis? ('Escaping' means that an object can be accessed after the method completes) A couple of examples on how an object can escape a method call: 1) The method returns the object that was locally created:

public MyObject someMethod(){
MyObject localObject = new MyObject();
return localObject();
}

//Another thread can now mutate this object because it has a reference to it:
someMethod.changeSomething();

2. One of the methods called with the LocalObject as parameter, stores the LocalObject instance in a way that allows access to it from other threads.

     MyMember member;          
   
     public void someMethod(){  
         LocalObject localObject = new LocalObject();  
   
         localObject.callMethod();  
         method2(localObject);  
     }  
   
     public void method2(LocalObject localObject){  
         localObject.setValue("value");  
         member = localObject;  
     }  
   

Does anyone know any more practical examples on how an object can escape a method call?

[jschell]

Neo10101 wrote:

//Another thread can now mutate this object because it has a reference to it:

No it can't. Not from that method. Thread 1 calls that method. That method create a brand spanking new object and returns it to the caller. Thread 2 calls that method. That method create a brand spanking new object and returns it to the caller. Neither object is the same. The calling sequence of the threads 1 and 2 are irrelevant (again in the context of this method only) each will still get a new object which is untouchable by the other thread.

Neo10101 wrote:

Does anyone know any more practical examples on how an object can escape a method call?

The method returns a data member of the class which is an object. So public MyObject getMyObject() { return myObject; }