Jira is one of the popular bug tracking tool developed by Atlassian. It also provides project management features inline with Agile methodology. Jira is basically written in Java & can integrate with source control programs like Perforce, Git, Clearcase, Subversion, TFS etc.
It also provides robust set of APIs which enables its integration with any system.
An interesting fact about its name 'JIRA': It is not an acronym, but a truncation of 'Gojira', the japanese name for 'Godzilla'. :)
Example to Create Issue & Search Issue:
This example shows how to consume Jira REST APIs from Java using REST Assured libraries.
NOTE: For the set up / usage of REST assured libraries can be found in another post.
https://advancedtestautomation.blogspot.in/2016/08/test-rest-web-services-using-rest.html