let java prefer ipv6 or ipv4

prefer IPv6 

export JAVA_OPTS="-Djava.net.preferIPv4Stack=false"

export _JAVA_OPTIONS="-Djava.net.preferIPv6Addresses=true"

prefer IPv4

export _JAVA_OPTIONS="-Djava.net.preferIPv4Stack=true";

export JAVA_OPTS="-Djava.net.preferIPv6Addresses=false";