Ant giving _JAVA OPTIONS message

Question

I have installed Apache Ant 1.8 on Windows 8.1.

When I am running the ant command on console, it is showing following message on screen:
Picked up _JAVA_OPTIONS: -Djava.net.preferIPv4Stack=true

I am not able to find the reason of this message.

Attaching screen shot for your reference.

Please provide me your comments on this. Also will it impact on the working of ant?

Please ignore the error about build.xml and 'tools.jar.

Answer 1

When I am running the ant command on console, it is showing following message on screen: Picked up _JAVA_OPTIONS: -Djava.net.preferIPv4Stack=true

I am not able to find the reason of this message.

_JAVA_OPTIONS is a special environment variable. It will be picked up by JVM. You are setting java.net.preferIPv4Stack to true means, disabling IPV6.

export _JAVA_OPTIONS=-Djava.net.preferIPv4Stack=true

You can achive the same using

System.setProperty("java.net.preferIPv4Stack" , "true");

through the code level in the application.

IPv6-Related System Properties

On dual stack machines, system properties are provided for setting the preferred protocol stack—IPv4 or IPv6—as well as the preferred address family types—inet4 or inet6.

IPv6 stack is preferred by default, since on a dual-stack machine IPv6 socket can talk to both IPv4 and IPv6 peers.

This setting can be changed through the java.net.preferIPv4Stack=<true|false> system property.

By default, we would prefer IPv4 addresses over IPv6 addresses, i.e., when querying the name service (e.g., DNS service), we would return Ipv4 addresses ahead of IPv6 addresses.

Check here for about Networking IPv6 User Guide for JDK/JRE 5.0.

BTW, That's not responsible for your error there. From your error message, there is no build.xml file in the directory, it seems.