Calling Java from Python

pip install JPype1

examples/python/java.py

from jpype import startJVM, shutdownJVM, java
#startJVM(getDefaultJVMPath(), "-ea")
startJVM(convertStrings=False)
java.lang.System.out.println("hello world")

random = java.util.Random()
number1 = random.nextInt(10)
number2 = random.nextInt(10)
print(number1, number2)
shutdownJVM()

See the jpype userguide

I tried this Python 3.7.3 running on Linux.

$ java -version
openjdk version "1.8.0_242"
OpenJDK Runtime Environment (build 1.8.0_242-8u242-b08-0ubuntu3~19.10-b08)
OpenJDK 64-Bit Server VM (build 25.242-b08, mixed mode)

$ sudo apt-get install openjdk-8-jdk-headless

$ javac -version
javac 1.8.0_242

examples/python/java1/Calculator.java

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

examples/python/java1/org/pkg/MyMath.java

package org.pkg;

public class MyMath {
    public static Integer divide(Integer a, Integer b) {
        return a/b;
    }
}

examples/python/java1/calc.py

from jpype import startJVM, shutdownJVM, java, addClassPath, JClass, JInt
startJVM(convertStrings=False)
import jpype.imports
#addClassPath("org/pkg")
#from org.pkg import MyMath
#import MyMath
#import org.pkg as p
#print(p)
#print(p.__class__)

try:
    pass
    #print(dir(p))
    #p.MyMath.divide(6, 2)
    #import Calculator
    calc = JClass('Calculator')
    print(calc)
    print(dir(calc))
    res = calc.add(java.lang.Integer(2), java.lang.Integer(2))
    print(res)
    #from org.pkg import Calculator
    math = JClass('org.pkg.MyMath')
    res = math.divide(java.lang.Integer(6), java.lang.Integer(2))
    #res = math.divide(JInt(6), java.lang.Integer(2))
    print(res)

    #calc = Calculator()
    #print(calc)
except Exception as err:
    print(f"Exception: {err}")

javac Calculator.java
javac org/pkg/MyMath.java
python calc.py

Directory layout (before running javac):

.
├── calc.py
├── Calculator.java
└── org
    └── pkg
        └── MyMath.java