The OP is from 2011. So as of end of 2015 I would like mention that there is a new kid in town which claims to be numpy for java -> nd4j]. The nice thing is that nd4j is an abstraction layer on top of different libraries like blas. Depending on the size of your matrices there are underlying implementations twice as fast as numpy or jblas. And your code is real platform independent.

Answer from KIC on Stack Overflow
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GitHub
github.com › tensorflow › java-ndarray
GitHub - tensorflow/java-ndarray · GitHub
NdArray is a library exposing utilities for manipulating data in a n-dimensional space in Java.
Discussions

NDArray library
A lightweight option: Neureka (Disclosure: I'm the author) More on reddit.com
🌐 r/java
17
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November 3, 2023
NumPy equivalent for Java?
Python only needs NumPy because NumPy performs its tasks directly in C, which is way faster than Python. Java doesn't need something like that, as it's a partially compiled language with many parts of the base modules written directly in Assembly. Therefore the equivalent for NumPy in Java would simply be the standard Java math module More on reddit.com
🌐 r/learnjava
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November 4, 2021
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InfoWorld
infoworld.com › home › brandposts › bringing the world of deep learning to java
A Guide to Using NDArrays in Java | InfoWorld
December 8, 2020 - Leverage the NDArray from Deep Java Library (DJL) to write your NumPy code in Java and apply NDArray into a real-world application.
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DIVISIO
divis.io › en › 2020 › 05 › deep-java-learning-introduction-part-1-ndmanager-ndarray
Divisio | Deep Java Learning Introduction - Part 1: NDManager & NDArray
May 12, 2020 - The simplest way to create an NDArray is to wrap a single value in an NDArray. This can be a Java primitive, or a class that implements Number, such as Integer or Float. Unlike, for example, java.util.List, NDArray is not generic, so we cannot tell from the type what data is stored.
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TensorFlow
tensorflow.org › jvm › ndarray
NdArray  |  JVM  |  TensorFlow
The `NdArray` interface creates an abstraction between the physical storage of a data record, which can be linear or segmented, and its logical representation. In general, they achieve better performances than standard multi-dimensional arrays ...
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Djl
d2l.djl.ai › chapter_preliminaries › ndarray.html
2.1. Data Manipulation — Dive into Deep Learning 0.1.0 documentation
The mxnet-engine includes the ... in C++ will be downloaded automatically when DJL is first used. ... An ndarray represents a (possibly multi-dimensional) array of numerical values....
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Towards Data Science
towardsdatascience.com › ndarray-a-java-based-n-dim-array-toolkit-60b4035b10b8
NDArray — — a Java based N-Dim array toolkit | by Qing Lan | Towards Data Science
December 15, 2021 - This is now standard practice in many fields such as data science, graphics, and deep learning, but can be used in applications far beyond this. In Python, the standard library for NDArrays is called NumPy. However, there is no equivalent standard library in Java.
Find elsewhere
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GitHub
github.com › ninia › jep › blob › master › src › main › java › jep › NDArray.java
jep/src/main/java/jep/NDArray.java at master · ninia/jep · GitHub
* NDArrays only support Java primitive arrays as the underlying type of data. * The data can conceptually be multi-dimensional, but it must be represented as · * a one-dimensional array in Java to ensure the memory is contiguous. * </p> * · * · * @author Nate Jensen ·
Author: ninia
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Javadoc.io
javadoc.io › doc › ai.djl › api › latest › ai › djl › ndarray › NDArray.html
NDArray - api 0.36.0 javadoc
https://javadoc.io/doc/ai.djl/api · Current version 0.36.0 · https://javadoc.io/doc/ai.djl/api/0.36.0 · package-list path (used for javadoc generation -link option) https://javadoc.io/doc/ai.djl/api/0.36.0/package-list ·
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Reddit
reddit.com › r/java › ndarray library
r/java on Reddit: NDArray library
November 3, 2023 -

I'm looking for a NDArray library in java that has many features similar to numpy. I mostly need element-wise operations, but also matrix manipulations like stack, flatting, concating etc. I need it to have very high performance as I will have thousands of calculations per second. My matrices will be about 500x500 (at average) So far I've tried many pure java libraries like EJML and commons math, but they lack many features. I also tried to use nd4j, but I'm getting a lot of memory leaks and very little support from their community.

Any suggestions? :)

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Konduit
deeplearning4j.konduit.ai › nd4j › overview
Overview | Deeplearning4j
June 15, 2026 - Backend transparency: The same Java code runs on CPU or GPU. No conditional logic, no separate code paths. org.nd4j.linalg.api.ndarray.INDArray is the central abstraction.
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Javatpoint
javatpoint.com › numpy-ndarray
NumPy Ndarray - Javatpoint
NumPy Ndarray with NumPy Introduction, Environment Setup, ndarray, Data Types, Array Creation, Attributes, Existing Data, Indexing and Slicing, Advanced Indexing, Broadcasting, Array Manipulation, Matrix Library, Matplotlib etc.
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Ninia
ninia.github.io › jep › javadoc › 3.8 › index.html
NDArray
JavaScript is disabled on your browser · Frame Alert · This document is designed to be viewed using the frames feature. If you see this message, you are using a non-frame-capable web client. Link to Non-frame version
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TensorFlow
tensorflow.org › jvm › ndarrays
NdArrays  |  JVM  |  TensorFlow
November 29, 2021 - From class java.lang.Object · Creates an N-dimensional array of booleans of the given shape. All values are initialized to zeros. new boolean N-dimensional array · Creates an N-dimensional array of bytes of the given shape.
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Apache
tvm.apache.org › docs › reference › api › javadoc › org › apache › tvm › NDArray.html
NDArray (TVM4J Package - Core 0.0.1-SNAPSHOT API)
Lightweight NDArray class of TVM runtime. ... Return a copied flat java array of current array (row-major).