In this work we present Vul4J, a Java vulnerability dataset where each vulnerability is associated to a patch and, most importantly, to a Proof of Vulnerability (PoV) test case. We analyzed 1803 fix commits from 912 real-world vulnerabilities in the Project KB knowledge base to extract the reproducible vulnerabilities, i.e., vulnerabilities that can be triggered by one or more PoV test cases. To this aim, we ran the test suite of the application in both, the vulnerable and secure versions, to identify the corresponding PoVs. Furthermore, if no PoV test case was spotted, then we wrote it ourselves. As a result, Vul4J includes 79 reproducible vulnerabilities from 51 open-source projects, spanning 25 different Common Weakness Enumeration (CWE) types. To the extent of our knowledge, this is the first dataset of its kind created for Java. Particularly, it targets the study of Automated Program Repair (APR) tools, where PoVs are often necessary in order to identify plausible patches. We made our dataset and related tools publically available on GitHub.