Comment 0 for bug 1780345

The tomcat8 init script contains:

find_jdks()
{
    for java_version in 9 8
    do
        for jvmdir in /usr/lib/jvm/java-${java_version}-openjdk-* \
                      /usr/lib/jvm/jdk-${java_version}-oracle-* \
                      /usr/lib/jvm/jre-${java_version}-oracle-* \
                      /usr/lib/jvm/java-${java_version}-oracle
        do
            if [ -d "${jvmdir}" ]
            then
                JDK_DIRS="${JDK_DIRS} ${jvmdir}"
            fi
        done
    done
}

# The first existing directory is used for JAVA_HOME (if JAVA_HOME is not
# defined in $DEFAULT)
JDK_DIRS="/usr/lib/jvm/default-java"
find_jdks

When the default-jre package is installed, this detects Java 11, but when it isn't, it doesn't.

# apt install tomcat8 openjdk-11-jre-headless
# /etc/init.d/tomcat8 start
 * no JDK or JRE found - please set JAVA_HOME

This was fixed in Debian in 8.5.31-1