You are developing an application that includes a class named Kiosk. The Kiosk class includes a static
property named Catalog. The Kiosk class is defined by the following code segment. (Line numbers are
included for reference only.)
You have the following requirements:
-Initialize the _catalog field to a Catalog instance.
-Initialize the _catalog field only once.
-Ensure that the application code acquires a lock only when the _catalog object must be instantiated.
You need to meet the requirements.
Which three code segments should you insert in sequence at line 09? (To answer, move the appropriate
code segments from the list of code segments to theanswer area and arrange them in the correct order.)
Answer:
Explanation:
This question is the same as 22.
No, it’s not
correct answer for thread safty:
get{
lock(_lock)
{
if(_catalog == null)
_catalog = new Catalog();
}
}
should be
get{
if(_catalog == null){
lock(_lock)
{
if(_catalog == null)
_catalog = new Catalog();
}
}
}
no need to lock if the instance is already created.
yeah you should actually, since this is a static object we’re trying to access
I may be wrong, but considering the
‘-Ensure that the application code acquires a lock only when the _catalog object must be instantiated.’
clause, I can’t see any other justifiable answer that
if (_catalog == null)
lock (_lock)
if (_catalog == null) _catalog = new Catalog();
, regardless of the correctness of the code.