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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Stack Overflow
stackoverflow.com › questions › 8375558 › java-equivalent-for-the-numpy-multi-dimensional-object
multidimensional array - Java equivalent for the Numpy multi-dimensional object - Stack Overflow
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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.

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The library Vectorz (https://github.com/mikera/vectorz) offers a fully featured NDArray that is broadly equivalent in functionality to Numpy's NDArray, i.e. it offers the fullowing features:

  • Arbitrary N-dimensional arrays of numeric values (in this case, Java doubles)
  • Lightweight views using strided access for efficient slicing
  • A broad range of mathematical operations with effiecient implementations

It's also very fast: it is much faster then NumPy for most operations, although NumPy may still be faster for certain large matrix operations because it uses the native BLAS libraries to accelerate these.

Here's the NDArray class itself:

https://github.com/mikera/vectorz/blob/develop/src/main/java/mikera/arrayz/NDArray.java

Disclaimer: I'm the author of Vectorz

Multidimension Array In Java
Multi-dimensional arrays in Java
java - multidimensional arrays and methods
python - Handling Multidimensional Arrays in Numpy
python - Numpy Multidimensional Array
More results from stackoverflow.com
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Reddit
reddit.com › r/learnjava › numpy equivalent for java?
r/learnjava on Reddit: NumPy equivalent for Java?
November 4, 2021 -

Is the a NumPy equivalent for Java?

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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
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I don't think there is a single Java library that covers so much functionality. I've seen Parallel Colt library originated at CERN, it should contain at least the basic pieces.
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Beyondthelines
beyondthelines.net › machine-learning › nd4j-numpy-for-the-jvm
Nd4j – Numpy for the JVM – Beyond the lines
JavaCPP also manages the off-heap memory where the data (tensors/matrices/…) are stored. Now that we’re all setup let’s see how the code looks like with a very basic example: ... val ones = Nd4j.create(3, 2) // 3 x 2 matrix filled with 0s ones.addi(1.0) // addi stands for add in-place println(s"ones: \n$ones") val matrix = Nd4j.create( Array(1.0, 2.0, 3.0, 4.0, 5.0, 6.0), // the values Array(3, 2), // dimensions: 3 x 2 'c' // 'c' c-style (row major) ) println(s"matrix: \n$matrix") val result = ones.transpose mmul matrix // onesT x matrix println(s"result: \n$result")
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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 - In Python, the standard library for NDArrays is called NumPy. However, there is no equivalent standard library in Java. One offering for Java developers interested in working with NDArrays is AWS’s Deep Java Library (DJL).
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Reddit
reddit.com › r/java › numpy equivalent for java?
r/java on Reddit: NumPy equivalent for Java?
November 4, 2021 - it does have some datatypes in (such as biginteger) but the the collections (similar to some found in numpy) are in java.util
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Stack Exchange
softwarerecs.stackexchange.com › questions › 43154 › java-equivalent-to-numpy
math - Java equivalent to NumPy - Software Recommendations Stack Exchange
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The nd4j.org API tries to mimic the semantics of Numpy, Matlab and scikit-learn. deeplearning4j.org is based on nd4j.

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NM Dev is a Java numerical library (commercial, community and academical licenses ).

The open source of it is available at: https://github.com/nmdev2020/SuanShu

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Stack Overflow
stackoverflow.com › questions › 57536534 › is-there-any-java-equivalent-of-numpy
python - Is there any Java equivalent of NumPy? - Stack Overflow
In anyway, you can find here an example of using numpy from Java using MetaFFI.
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DEV Community
dev.to › darius_nica › introducing-numpy4j-bringing-numpy-style-computing-tojava-3gha
Introducing NumPy4J: Bringing NumPy-Style Computing toJava - DEV Community
July 22, 2026 - I wanted a similar experience in Java: a lightweight, dependency-free library for working with multidimensional arrays and linear algebra. That idea became NumPy4J.
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NumPy
numpy.org › doc › 2.2 › reference › generated › numpy.ones_like.html
numpy.ones_like — NumPy v2.2 Manual
>>> y = np.arange(3, dtype=float) >>> y array([0., 1., 2.]) >>> np.ones_like(y) array([1., 1., 1.])
Find elsewhere
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Reddit
reddit.com › r/java › what are the best java libraries for data analysis and machine learning?
r/java on Reddit: What are the best Java libraries for data analysis and machine learning?
December 18, 2017 -

Basically I am looking for equivalent of Python’s NumPy, SciPy, pandas, scikit-learn and Keras.

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JSAT is totally the indisputably best ML library for Java. I'm not 1000% biased because I wrote it or anything.

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Some are not Java but run-on the JVM

https://spark.apache.org/

https://software.intel.com/en-us/intel-daal

http://mxnet.incubator.apache.org/

https://mahout.apache.org/

https://flink.apache.org/

http://ranksys.org/

https://deeplearning4j.org/

https://www.h2o.ai/

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Reddit
reddit.com › r/learnjava › what is comparable to python pandas and numpy in java?
r/learnjava on Reddit: What is comparable to Python Pandas and Numpy in Java?
October 12, 2020 -

I'm looking to build an application which connects to a SQL Server database, manipulates data pulled from it, reads an excel file, manipulates data inside it and writes a CSV file (to be read by some other application).

I've created a program that does exactly this in Python using pandas and numpy.

What are comparable Java packages/modules?

Side note: I know very little Java and figure this could be a good first project for me.

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https://github.com/cardillo/joinery

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Imagej
py.imagej.net › en › latest › 03-Sending-Data-to-Java.html
3 Converting to Java: ij.py.to_java() — PyImageJ documentation
The function ij.py.to_java() is capable of converting common Python and NumPy data types into their Java/ImageJ equivalent. There is one important nuance; converting a NumPy array to Java creates a Java object that points to the NumPy array.
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GitHub
github.com › JosephCottam › Numpy4J
GitHub - JosephCottam/Numpy4J: Interface Java with Numpy. Try to be reasonable. · GitHub
What works: If you make an NPArray (that's the Java class that represents a Numpy array), you can execute max, min, log and array-array multiply. For log and multiply, the resulting NPArray is actually backed by memory that numpy allocated for ...
Starred by 56 users
Forked by 5 users
Languages: Java 53.0% | C 40.1% | Python 6.0% | C++ 0.9%
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JAX Documentation
docs.jax.dev › en › latest › _autosummary › jax.numpy.ones_like.html
jax.numpy.ones_like — JAX documentation
>>> x = jnp.arange(4) >>> jnp.ones_like(x) Array([1, 1, 1, 1], dtype=int32) >>> jnp.ones_like(x, dtype=bool) Array([ True, True, True, True], dtype=bool) >>> jnp.ones_like(x, shape=(2, 3)) Array([[1, 1, 1], [1, 1, 1]], dtype=int32)
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Stack Overflow
stackoverflow.com › questions › 7205154 › any-java-math-library-allowing-vectorization-and-broadcasting-the-way-numpy-does
Any Java math library allowing vectorization and broadcasting the way numpy does? - Stack Overflow
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1 of 2
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I had the same problem as you but did not find a java solution. Java misses operator overloading for [] and has no slices. So you will not find a Java solution with the same, easy to read notation as numpy provides.

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The nd4j library is essentially "NumPy for Java". It supports broadcasting and vector operations.

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w3resource
w3resource.com › numpy › array-creation › ones_like.php
NumPy: numpy.ones_like() function - w3resource
April 21, 2026 - The numpy.ones_like() function is used to get an array of ones with the same shape and type as an existing array.
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GitHub
github.com › GreenDelta › npy
GitHub - GreenDelta/npy: npy is a Java 11+ library for reading and writing arrays in the NumPy NPY and NPZ format. · GitHub
npy is a Java 11+ library for reading and writing arrays in the NumPy NPY and NPZ format. - GreenDelta/npy
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ResearchGate
researchgate.net › post › What_libraries_would_make_Java_easy_to_use_for_scientific_computing
What libraries would make Java easy to use for scientific computing? | ResearchGate
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Just one thought : Java was created in order to make applets/apps portable. A java application is therefore supposed to be "independent" from the hardware (beside the fact that the JVM is obviously compiled for a given architecture, but the API remains the same across architectures). You can use/call native code through the JNI interface, but this makes often your app non portable. Beside this, I agree with Thomas. I personally wrote several traffic assignment algorithms on very large networks using parallel threads in Java. I agree that before 2002/2003 this would not have been possible, but modern JVM/HotSpot has comparable performances to C++. This being said, did you have a look to Apache Common Math ? http://commons.apache.org/proper/commons-math/ This library is well written and supported...
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I know of one JAVA project called JAS (Java Algebra system) useful for symbolic computation. There is also JAMA for doing matrix computations in JAVA and Jampack, look also in Google. For plotting I found jmathplot. As for my personal experience, speed for scientific computations with JAVA is ok and can compete with any other high-level programming language. Only thing you have to take care is memory requirements as you would have to adjust the heap size of Java virtual machine. Otherwise, there should be same kind of obstacles in scientific computing to Java programs than also to other high-level programming languages.
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GitHub
github.com › jpype-project › jpype › issues › 1341
Documentation: best way to access numpy arrays from Java without copying · Issue #1341 · jpype-project/jpype · GitHub
February 3, 2026 - – I could not find instructions on how to zero-copy map an existing numpy array to Java; but I'd imagine that a lot of users will be looking for this.
Author: jpype-project
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Medium
hakmesyo.medium.com › ojl-java-and-numpy-python-performance-benchmark-on-massive-matrix-operations-7127345116e4
OJL (Java) and Numpy (Python) performance benchmark on massive matrix operations | by Musa Ataş | Medium
November 6, 2022 - OJL (Java) and Numpy (Python) performance benchmark on massive matrix operations OJL, also known as the Open Jazari Library, https://github.com/hakmesyo/open-jazari-library is a library developed in …