Update Dockerfile

Dockerfile

@@ -1,5 +1,4 @@
-# Use an Ubuntu base image
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 # Set environment variables
 ENV NB_USER=jovyan
@@ -7,7 +6,7 @@ ENV NB_UID=1000
 ENV HOME=/home/${NB_USER}
 ENV JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/
 
-# Install Python 3.4 and dependencies
+# Install required system packages and Python 3.6
 RUN apt-get update && apt-get install -y \
     software-properties-common \
     wget \
@@ -24,20 +23,20 @@ RUN apt-get update && apt-get install -y \
     pkg-config \
     graphviz \
     openjdk-8-jdk \
-    python3.4 \
-    python3.4-dev \
+    python3.5 \
+    python3.5-dev \
     python3-pip \
     ant \
     ca-certificates \
     && apt-get clean \
     && update-ca-certificates -f
 
-# Set up JAVA_HOME for OpenJDK 8
-RUN echo "export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64/" >> /etc/profile \
-    && echo "export PATH=\$JAVA_HOME/bin:\$PATH" >> /etc/profile
+# Upgrade pip for Python 3.6
+RUN python3.5 -m pip install --upgrade pip setuptools
 
-# Upgrade pip for Python 3.4 (using an older version of pip)
-RUN python3.4 -m pip install --upgrade pip==9.0.3 setuptools==44.1.1
+# Install Python dependencies
+COPY requirements.txt /tmp/requirements.txt
+RUN python3.5 -m pip install --no-cache-dir -r /tmp/requirements.txt
 
 # Create a new user
 RUN useradd -m -u ${NB_UID} ${NB_USER}
@@ -49,10 +48,6 @@ USER ${NB_USER}
 ENV HOME=/home/${NB_USER}
 ENV PATH=/home/${NB_USER}/.local/bin:$PATH
 
-# Install Python dependencies from requirements.txt
-COPY requirements.txt /tmp/requirements.txt
-RUN python3.4 -m pip install --no-cache-dir -r /tmp/requirements.txt
-
 # Copy application code to the container
 COPY --chown=${NB_USER}:${NB_USER} . ${HOME}