---
license: mit
task_categories:
- text-generation
tags:
- code
- java
- refactoring
- benchmark
- software-engineering
size_categories:
- n<1K
dataset_info:
  features:
  - name: instance_id
    dtype: string
  - name: repo
    dtype: string
  - name: resource_tier
    dtype: string
  - name: repo_stars
    dtype: float64
  - name: repo_forks
    dtype: float64
  - name: language
    dtype: string
  - name: base_commit
    dtype: string
  - name: merge_commit
    dtype: string
  - name: refactoring_types
    list: string
  - name: refactoring_descriptions
    list: string
  - name: file_path
    dtype: string
  - name: source_code_before
    dtype: string
  - name: source_code_after
    dtype: string
  - name: diff
    dtype: string
  - name: is_pure_refactoring
    dtype: bool
  - name: compile_before
    dtype: bool
  - name: compile_after
    dtype: bool
  - name: tests_pass_before
    dtype: bool
  - name: tests_pass_after
    dtype: bool
  - name: FAIL_TO_PASS
    list: string
  - name: PASS_TO_PASS
    list: string
  - name: created_at
    dtype: string
  - name: repo_license
    dtype: string
  - name: lines_changed
    dtype: float64
  splits:
  - name: test
    num_bytes: 279451236
    num_examples: 816
  download_size: 245967508
  dataset_size: 279451236
configs:
- config_name: default
  data_files:
  - split: test
    path: data/test-*
---

# CS4570 Java Refactoring Benchmark

A benchmark of Java refactoring commits mined from GitHub repositories, split into **high-resource** and **low-resource** tiers based on repository popularity. Built for the TU Delft CS4570 ML for Software Engineering course (2026).

## Dataset split

| Tier | Repositories | Instances | Star range |
|------|-------------|-----------|------------|
| High-resource | 57 | 618 | 1000-7298 |
| Low-resource | ~60 | 198 | 13-90 |
| **Total** | | **816** | |

Use the `resource_tier` field to filter by tier. `repo_stars` and `repo_forks` are included for fine-grained popularity analysis.

## Construction

Each instance is a single-file refactoring commit that was:

1. Detected by **RefactoringMiner 3.1.3** as containing at least one Java refactoring operation
2. Verified by building the project before and after the commit using Docker (Maven/Gradle, JDK 17/21)
3. Filtered to commits where the project compiles and tests pass both before and after (pure refactorings)

High-resource repos have >=1000 stars and >=10 contributors; low-resource repos have <100 stars.

## Fields

| Field | Type | Description |
|-------|------|-------------|
| `instance_id` | string | Unique identifier |
| `repo` | string | owner/repo identifier |
| `resource_tier` | string | "high" or "low" |
| `repo_stars` | int or null | GitHub star count at collection time |
| `repo_forks` | int or null | GitHub fork count at collection time |
| `language` | string | Always "java" |
| `base_commit` | string | Parent commit SHA |
| `merge_commit` | string | Refactoring commit SHA |
| `refactoring_types` | list[str] | Refactoring type labels from RefactoringMiner |
| `refactoring_descriptions` | list[str] or null | Human-readable descriptions (HR only) |
| `file_path` | string | Java file path that was refactored |
| `source_code_before` | string | File content at base commit |
| `source_code_after` | string | File content at merge commit |
| `diff` | string | Unified diff between before and after |
| `is_pure_refactoring` | bool or null | True if only refactoring operations changed |
| `compile_before` | bool or null | Project compiled at base commit |
| `compile_after` | bool or null | Project compiled at merge commit |
| `tests_pass_before` | bool or null | All tests pass at base commit |
| `tests_pass_after` | bool or null | All tests pass at merge commit |
| `FAIL_TO_PASS` | list[str] | Tests failing before, passing after |
| `PASS_TO_PASS` | list[str] | Tests passing both before and after |
| `created_at` | string or null | Commit timestamp (ISO 8601) |
| `repo_license` | string or null | SPDX license identifier |
| `lines_changed` | int or null | Lines changed in the refactoring |

## Refactoring types

Top types across both tiers: Extract Method, Rename Method, Rename Variable, Rename Parameter, Extract Variable, Inline Variable, Change Variable Type, Add Parameter, Add Method Annotation, Rename Attribute.

66 unique refactoring types in total.

## Usage

```python
from datasets import load_dataset

ds = load_dataset("Maxros/test", split="test")

# Filter by tier
hr = ds.filter(lambda x: x["resource_tier"] == "high")
lr = ds.filter(lambda x: x["resource_tier"] == "low")
```

## Citation

```
TU Delft CS4570 -- ML for Software Engineering benchmark, 2026.
```