Simplify Java Stream Processing with JDFrame: A Semantic DataFrame Alternative

Introduction: The author created a JVM-level DataFrame‑like tool to provide a more semantic and concise API for Java 8 streams, inspired by Spark and pandas.

Quick Start

Dependency

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

Example

Calculate the total score of schools where students are aged 9‑16, then list the top two schools.

static List<Student> studentList = new ArrayList<>();
// ... add Student objects ...
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(2);
sdf2.show();

Output:

三中 10
二中 7

API Overview

Matrix view

void show(int n);
List<String> columns();
List<R> col(Function<T,R> function);
T head();
List<T> head(int n);
T tail();
List<T> tail(int n);
List<T> page(int page, int pageSize);

Filtering

whereBetween(...);
whereBetweenR(...);
whereBetweenL(...);
whereNotNull(...);
whereGt(...);
whereGe(...);
whereLt(...);
whereIn(...);
whereNotIn(...);
whereEq(...);
whereNotEq(...);
whereLike(...);
whereLikeLeft(...);
whereLikeRight(...);

Aggregation

max(...);
maxValue(...);
min(...);
minValue(...);
avg(...);
sum(...);
maxMin(...);
maxMinValue(...);

Distinct, Grouping, Joining, Pagination, etc.

Methods such as distinct(), groupBySum(), join(), cutFirst(), defaultScale() and others provide SQL‑like semantics for deduplication, grouping, joins, slicing and result formatting.

SDFrame vs JDFrame

SDFrame behaves like a lazy Java Stream—operations take effect only after a terminal call—while JDFrame applies changes immediately, allowing intermediate results to be inspected without re‑reading the data.

Author: 李白的手机 Source: juejin.cn/post/7356652717392740404