Using structural relationships to facilitate api learning

Application Programming Interfaces (APIs) allow software developers to reuse code libraries, frameworks, or services without the need of having to implement relevant functionalities from scratch. The benefits of reusing source code or services through APIs have encouraged the adoption of APIs as the building blocks of modern-day software systems. However, leveraging the benefits of APIs require a developer to frequently learn how to use unfamiliar APIs — a process made difficult by the increasing size of APIs, and the increase in the number of APIs with which a developer has to work. In this dissertation, we investigated some of the challenges developers encounter when working with unfamiliar APIs, and we designed and implemented new programming tools to assist developers in learning how to use new APIs.To investigate the difficulties developers encounter when learning to use APIs, we conducted a programming study in which twenty participants completed two programming tasks using real-world APIs. Through a systematic analysis of the screen captured videos and the verbalizations of the participants, we isolated twenty different types of questions the programmers asked when learning to use APIs, and identified five of the twenty questions as the most difficult for the programmers to answer in the context of our study. Drawing from varied sources of evidence, such as the verbalizations and the navigation paths of the participants, we explain why the participants found certain questions hard to answer, and provide new insights to the cause of the difficulties. To facilitate the API learning process, we designed and evaluated two novel programming tools: API Explorer and Introspector. The API Explorer tool addresses the difficulty a developer faces when the API types or methods necessary to implement a task are not accessible from the type the developer is working with. API Explorer leverages the structural relationships between API elements to recommend relevant methods on other objects, and to identify API types relevant to the use of a method or class. The Introspector tool addresses the difficulty of formulating effective queries when searching for code examples relevant to implementing a task. Introspector combines the structural relationships between API types to recommend types that should be used together with a seed to search for code examples for a given task. Using the types recommended by Introspector as search query, a developer can search for code examples across two code repositories, and in return, will get a list of code examples ranked based on their relevance to the search query. We evaluated API Explorer through a programming study, and evaluated Introspector quantitatively using ten tasks from six different APIs. The results of the evaluations suggest that these programming tools provide effective support to programmers learning how to use APIs.