JDFrame/SDFrame Java DataFrame Library: API Guide and Usage Examples

The JDFrame and SDFrame libraries bring a DataFrame‑style, semantic API to Java 8 streams, allowing developers to write concise, SQL‑like data manipulation code without hard‑coding field names. The article begins with a free book promotion and then explains the motivation for creating a JVM‑level DataFrame tool.

Quick Start – Add the Maven dependency:

<dependency>
    <groupId>io.github.burukeyou</groupId>
    <artifactId>jdframe</artifactId>
    <version>0.0.6</version>
</dependency>

Then create a list of Student objects and use the library to perform queries such as counting students aged 9‑16 and retrieving the top two schools by total score.

Example Query :

SDFrame<FI2<String, BigDecimal>> sdf2 = SDFrame.read(studentList)
    .whereNotNull(Student::getAge)
    .whereBetween(Student::getAge, 9, 16)
    .groupBySum(Student::getSchool, Student::getScore)
    .sortDesc(FI2::getC2)
    .cutFirst(10);

sdf2.show();

The output shows the aggregated scores per school.

API Overview – The library provides methods for matrix viewing, filtering ( whereBetween, whereEq, whereLike), distinct operations, grouping and aggregation ( groupBySum, groupByMax, groupByCount), sorting ( sortDesc, sortAsc), joining ( join, leftJoin, rightJoin), pagination, row numbering, and replenishing missing dimension values.

Additional features include percentage conversion, partitioning a list into sub‑lists, and setting default numeric scale. The article concludes with a comparison between SDFrame (lazy, stream‑like) and JDFrame (eager, DataFrame‑like) and invites readers to suggest further API ideas.