How to Call Java using Python with JPype and Pyjnius

Calling Java using Python Title
Calling Java With Python

We are all very familiar with Java and Python programming languages. But both have their own pros and cons. What if we combined them and used the best of both worlds and started to call Java using Python. We can use Java’s existing packages, frameworks, libraries, and more that are more challenging to implement in Python or are simply not available.
Hence, We need to Integrate Python and Java to avail benefits of a wide range of tools and resources provided by both languages. The biggest use of this will be that developers can now enjoy Java’s extensive ecosystem while doing it with the simplicity and ease of Python Programming.

We will be taking a look at how to call Java in Python using JPype and Pyjnius and other ways, Cover the advantages of calling Java using Python, use case scenarios, and The challenges and limitations faced along the way.

Java Using Python
Java Using Python


Java is a widely used, high-level programming language that was developed by James Gosling of Sun Microsystems in the mid-1990s. Java is widely known for its “write once, run anywhere” approach of Platform Independence. This was made possible by its JVM, which can be run on any system.
Java is the most widely used language in billions of mobile devices, and It has an Object-oriented approach programming to it with a simple syntax similar to that of C++.
Applications of Java are web development, mobile app development, and many more.


Python is a high-level programming language developed by Guido van Rossum in the late 1980s. It is based on simplicity and readability because of its simple, clear, and concise syntax that allows developers to easy, fast, and reliable Development.
Python supports multiple programming paradigms, like object-oriented, functional, and procedural styles of development. Over the years, it has built up a large audience and publicity as one of the easiest and most convenient languages to develop programs. Applications of Python are in the fields of web development, data analytics, etc.

Overview of Integration Methods:

Calling Java using Pythons (JPype Method):

What is JPype Library?

JPype library is a Python library that facilitates Python developers with the integration of Java code into their Python applications. It acts like a bridge between Python and Java, allowing Python programs to interact with Java classes, methods, objects, and packages.
JPype can be used to access existing Java libraries and Java code within your Python projects.

Installing and setting up JPype:

To Install JPype in your system, use the following cmd command:

pip install JPype1

To Import JPype1 into your programs, you can use the following:

import jpype
import jpype.imports

Example of Using JPype


from jpype import startJVM, shutdownJVM, java
java.lang.System.out.println("hello world")
random = java.util.Random()
number1 = random.nextInt(10)
number2 = random.nextInt(10)
print(number1, number2)


from jpype import startJVM, shutdownJVM, java, addClassPath, JClass, JInt
import jpype.imports
    calc = JClass('calci')
    res = calc.add(java.lang.Integer(2), java.lang.Integer(2))
    math = JClass('pkg.returnmath')
    res = math.divide(java.lang.Integer(6), java.lang.Integer(2))
except Exception as err:
    print(f"Exception: {err}")

In the file, we are importing some main methods from the Jpype library that we will need in further execution of the Java classes. We first start by starting the JVM and then take class variables of calci and store it into calc variable; then we print the directory of the calci class, and then we create a res variable for storing the addition of the integers, and then we print the result.
After that, we access the returnmath class from the pkg named package, and then we do the same for this too, and then we print the result of it too.
Lastly, we performed all this execution within the try block to avoid abrupt cancellation and instead opted for the exception-handling approach of development.


public class calci {
    public static Integer add(Integer a, Integer b) {
        return a*b;

In the we are creating a java class that will be returning a multiplication of the randomly generated numbers a and b.


package pkg;
public class returnmath {
    public static Integer divide(Integer a, Integer b) {
        return a/b;

In we are just creating a class that will be returning the division of the randomly generated numbers a and b.

Other Methods of Calling Java using Python:

Optionally we can use various other methods of implementing the above example using various approaches like using PyJnuis or using JCC libraries in Python that act as a bridge between the Python program and the java classes, libraries, or packages.
These Python libraries provide a very helpful and convenient way of implementing or calling Java using Python.

Benefits of Calling Java Using Python

There are many reasons to call Java using Python, and they are as follows:

  • Provides Access to Java Libraries
  • Seamless Integration
  • Allows Hybrid Development
  • Higher Cross-Platform Compatibility
  • Increased Performance Boost
  • Access to Java’s GUI Applications like swings
  • Extensive Community Support

Challenges and Limitations Faced while calling java using Python

  • Compatibility Issues: This may happen as versions may differ of Java and Python as well, as it can be more complex when the bridging library is not compatible with the existing language’s model.
  • Performance Overhead: Interfacing Python and Java may introduce performance bottlenecks or performance overheads when transferring data between the two languages.
  • Debugging Complexity: Debugging such an integrated program can be a mess as the languages have different syntaxes, as well as it, would require an expert in both languages to troubleshoot and debug any problems or bugs.
  • Resource Management: Properly managing all the resources, like Jvm instances and memory, can be very hard.
  • Affects Python’s readability and maintainability overall.
  • Limited Python Library Support: Some Python libraries may not work with java based components or libraries as they were not built to do so, leading to restrictions in development.


So far, we have seen how we can call Java using Python using Jpype.

It’s clear that this will be beneficial for us as we’ll be able to utilize the advantages of both languages. We can enjoy the straightforward syntax of Python while also having access to the extensive libraries and framework support of Java.

Calling java using python has its limitations too as it needs expertise of both languages to integrate both languages seamlessly and develop a program out of it.

But rest assured, it is a very viable option when it comes to customizability and platform independence, and we can’t deny all the further undiscovered possibilities that calling Java using Python may have.