  Third-party libraries are a central building block to develop software
systems. However, outdated third-party libraries are commonly used, and
developers are usually less aware of the potential risks. Therefore, a
quantitative and holistic study on usages, updates and risks of third-party
libraries can provide practical insights to improve the ecosystem sustainably.
In this paper, we conduct such a study in the Java ecosystem. Specifically, we
conduct a library usage analysis (e.g., usage intensity and outdatedness) and a
library update analysis (e.g., update intensity and delay) using 806
open-source projects. The two analyses aim to quantify usage and update
practices holistically from the perspective of both open-source projects and
third-party libraries. Then, we conduct a library risk analysis (e.g.,
potential risk and developer response) in terms of bugs with 15 popularly-used
third-party libraries. This analysis aims to quantify the potential risk of
using outdated libraries and the developer response to the risk. Our findings
from the three analyses provide practical insights to developers and
researchers on problems and potential solutions in maintaining third-party
libraries (e.g., smart alerting and automated updating of outdated libraries).
To demonstrate the usefulness of our findings, we propose a bug-driven alerting
system for assisting developers to make confident decisions in updating
third-party library versions. We have released our dataset to foster valuable
applications and improve the ecosystem.
