How Weak Reference is Used in Java Projects?

Many programming languages have a system of garbage collection to automate memory management. Problems such as unexpected memory leak still may occur due to the automation of memory management. Weak reference has been proposed as a solution to such problems. However, the use of weak reference often requires consideration of memory release timing, which is difficult for developers. In this study, we investigate the use of weak reference on open source projects. More concretely, we investigated the domain of software projects where the weak reference was used, the timing of the introduction of the weak reference, the usage method, the presence or absence of the test code for weak reference, and the case of failure to introduce weak reference in the Java language. The survey showed that weak references were used in 73 repositories, about one-third of the total 202 repositories, and that weak references were most common in test code.