Luck, mostly. However, libraries do tend to fall into 2 categories: small, and big. (yeah, I worked hard to come up with those) * Small, sharp tools (someti

Luck, mostly. However, libraries do tend to fall into 2 categories: small, and big. (yeah, I worked hard to come up with those) * Small, sharp tools (sometimes) - things like Google Guava "collections" utilities, or the Ostermiller CSV file handling library, which have very small and stable scope. * Big collections of things, such as Spring or Struts. Regardless of how you feel about these libraries, they do tend to come as a family of interrelated libraries (supplemental components) that get released in lock-step and play nice together. I dislike the Java language, but I guess it is nice that most of the stuff on Maven Central does tend to be stable.