Concurrency Problem in Double Check Locking

Question

Consider the `LazyInit` class shown below, which uses a double-check locking pattern to lazily initialize a `Resource` object. Which of the following statements best describes a potential concurrency problem in this implementation?

```java
public class LazyInit {
    private Resource resource = null;
    
    public Resource getResource() {
        if(resource == null) {
            synchronized(this) {
                if(resource == null) {
                    resource = new Resource();
                }
            }
        }
        return resource;
    }
}

class Resource {
    // Resource implementation
}
```

Accepted Answer

Without declaring 'resource' as volatile, threads might see a partially constructed Resource due to possible instruction reordering.

Answer

The variable 'resource' should be final to ensure thread safety, and its absence leads to immediate failure.

Answer

The nested if statements inherently cause a deadlock between competing threads.

Answer

Double-check locking is redundant when using synchronized, so no concurrency issue exists.

Question Leaderboard