avoid jdk-11.0.6+10: it shows problem "S8217731: Font rendering and glyph spacing changed from jdk-8 to jdk-11" https://bugs.openjdk.java.net/browse/JDK-8217731 even though the changelog claims to have resolved this;
#!/usr/bin/env bash
#
# Author: Makarius
#
# DESCRIPTION: invoke Java within the Isabelle environment
eval "declare -a JAVA_ARGS=($ISABELLE_JAVA_SYSTEM_OPTIONS)"
[ -n "$CLASSPATH" ] && classpath "$CLASSPATH"
unset CLASSPATH
isabelle_java java "${JAVA_ARGS[@]}" \
-classpath "$(platform_path "$ISABELLE_CLASSPATH")" "$@"