NPEX: Repairing Java Null Pointer Exceptions without Tests

Junhee Lee, Seongjoon Hong, Hakjoo Oh

Research output: Chapter in Book/Report/Conference proceedingConference contribution

5 Citations (Scopus)


We present NPEX, a new technique for repairing Java null pointer exceptions (NPEs) without tests. State-of-the-art NPE repair techniques rely on test suites written by developers for patch validation. Unfortunately, however, those are typically future test cases that are unavailable at the time bugs are reported or insufficient to identify correct patches. Unlike existing techniques, NPEX does not require test cases; instead, NPEX automatically infers the repair specification of the buggy program and uses the inferred specification to validate patches. The key idea is to learn a statistical model that predicts how developers would handle NPEs by mining null-handling patterns from existing codebases, and to use a variant of symbolic execution that can infer the repair specification from the buggy program using the model. We evaluated NPEX on real-world NPEs collected from diverse open-source projects. The results show that NPEX significantly outperforms the current state-of-the-art.

Original languageEnglish
Title of host publicationProceedings - 2022 ACM/IEEE 44th International Conference on Software Engineering, ICSE 2022
PublisherIEEE Computer Society
Number of pages13
ISBN (Electronic)9781450392211
Publication statusPublished - 2022
Event44th ACM/IEEE International Conference on Software Engineering, ICSE 2022 - Pittsburgh, United States
Duration: 2022 May 222022 May 27

Publication series

NameProceedings - International Conference on Software Engineering
ISSN (Print)0270-5257


Conference44th ACM/IEEE International Conference on Software Engineering, ICSE 2022
Country/TerritoryUnited States

Bibliographical note

Funding Information:
This work was partly supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government(MSIT) (No.2020-0-01337,(SW STAR LAB) Research on Highly-Practical Automated Software Repair and No.2021-0-00758, Development of Automated Program Repair Technology by Combining Code Analysis and Mining) and the MSIT(Ministry of Science and ICT), Korea, under the ICT Creative Consilience program (IITP-2022-2020-0-01819) supervised by the IITP(Institute for Information & communications Technology Planning & Evaluation), and the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIT) (No.2021R1A5A1021944).

Publisher Copyright:
© 2022 ACM.

ASJC Scopus subject areas

  • Software


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