Build OpenCV (with Java) from git sources on Ubuntu Linux

opencv-install.sh

# Install OS tools needed for the build
sudo apt-get -y update
sudo apt-get install -y build-essential cmake git libgtk2.0-dev pkg-config libavcodec-dev libavformat-dev libswscale-dev ant default-jdk

# Detect the default java home and set the env var for it
export JAVA_HOME=$(java -XshowSettings:properties -version 2>&1 > /dev/null | awk -F' ' '/java.home/ {print $3}')
export ANT_HOME=/usr/bin/ant

git clone https://github.com/opencv/opencv
cd opencv/
mkdir build
cd build
cmake -D BUILD_SHARED_LIBS=OFF ..
make -j$(nproc)

# Create a test program in Java
cat << EOF > ./HelloCV.java

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;

public class HelloCV
{
  public static void main (String[] args)
  {
    System.loadLibrary (Core.NATIVE_LIBRARY_NAME);
    Mat mat = Mat.eye (3, 3, CvType.CV_8UC1);
    System.out.println ("mat = " + mat.dump());
  }
}
EOF

# Detect the OpenCV jar file name
OPENCV_JAR=$(ls bin/opencv-*.jar)

# Build and run the test
javac -cp .:$OPENCV_JAR HelloCV.java
java -cp .:$OPENCV_JAR -Djava.library.path=lib HelloCV