Java: Fixing java.lang.UnsupportedClassVersionError and Unsupported major.minor version error!

Amazon I was reading http://docs.oracle.com/javase/tutorial/networking/nifs/parameters.html and decided to compile run the Java code listed on that webpage. Here is the code:

import java.io.*;
import java.net.*;
import java.util.*;
import static java.lang.System.out;

public class ListNetsEx {

    public static void main(String args[]) throws SocketException {
        Enumeration<NetworkInterface> nets = NetworkInterface.getNetworkInterfaces();
        for (NetworkInterface netint : Collections.list(nets))
            displayInterfaceInformation(netint);
    }

    static void displayInterfaceInformation(NetworkInterface netint) throws SocketException {
        out.printf("Display name: %s\n", netint.getDisplayName());
        out.printf("Name: %s\n", netint.getName());
        Enumeration<InetAddress> inetAddresses = netint.getInetAddresses();
        
        for (InetAddress inetAddress : Collections.list(inetAddresses)) {
            out.printf("InetAddress: %s\n", inetAddress);
        }
       
        out.printf("Up? %s\n", netint.isUp());
        out.printf("Loopback? %s\n", netint.isLoopback());
        out.printf("PointToPoint? %s\n", netint.isPointToPoint());
        out.printf("Supports multicast? %s\n", netint.supportsMulticast());
        out.printf("Virtual? %s\n", netint.isVirtual());
        out.printf("Hardware address: %s\n",
                    Arrays.toString(netint.getHardwareAddress()));
        out.printf("MTU: %s\n", netint.getMTU());
        out.printf("\n");
     }
}

I happily compiled the code with javac ListNetsEx.java and ran it with java ListNetsEx. To my dismay I got the following error message:

Exception in thread "main" java.lang.UnsupportedClassVersionError: <your Java class name> :
Unsupported major.minor version 52.0

It turns out my Java JRE runtime environment is newer than the Java program. How do I fix the Java exception java.lang.UnsupportedClassVersionError and Unsupported major.minor version error?

Solution

I began to look for a solution on the Internet. Somewhere online I found a solution, which is run the following command :

javac -target 1.7 ListNetsEx.java

But then I got the following error:

javac: target release 1.7 conflicts with default source release 1.8

The REAL solution is run the following command:

javac -target 1.7 -source 1.7 ListNetsEx.java

You will get a warning:

warning: [options] bootstrap class path not set in conjunction with -source 1.7
1 warning

But it is harmless. Now run the following command:

java ListNetsEx

and you should see the output!