Lazy initialization

In <a href="/facts/Computer_programming/QmSsFnu0">computer programming</a>, lazy initialization is the tactic of delaying the creation of an <a href="/facts/Object_(computer_science)/eX99dtAw">object</a>, the calculation of a <a href="/facts/Value_(computer_science)/QgQPbewf">value</a>, or some other expensive process until the first time it is needed. It is a kind of <a href="/facts/Lazy_evaluation/mD3DxDkc">lazy evaluation</a> that refers specifically to the instantiation of objects or other resources.
This is typically accomplished by augmenting an accessor method (or property getter) to check whether a private member, acting as a cache, has already been initialized. If it has, it is returned straight away. If not, a new instance is created, placed into the member variable, and returned to the caller just-in-time for its first use. 
If objects have properties that are rarely used, this can improve startup speed. Mean average program performance may be slightly worse in terms of memory (for the condition variables) and execution cycles (to check them), but the impact of object instantiation is spread in time ("amortized") rather than concentrated in the startup phase of a system, and thus median response times can be greatly improved.
In <a href="/facts/Multithreading_(computer_architecture)/ojEKsSNP">multithreaded</a> code, access to lazy-initialized objects/state must be <a href="/facts/Mutual_exclusion/1dwvCxDW">synchronized</a> to guard against <a href="/facts/Race_condition/bvNpgy4F">race conditions</a>.

Lazy initialization open-in-new

Lazy initialization