Java Networking 501 :)

gistfile1.java

package test;

import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.UnknownHostException;


/**
 * Demonstrate that InetAddress#getByName() with a literal does not
 * fill in the host name, which leads to (uncached) reverse lookups 
 * on InetAddress#getHostName().
 * <P>
 * This can be avoided by not using getHostName() or by creating the 
 * Object with InetAddress#getByAddr(String, byte[]).
 *
 * @author Bernd Eckenfels
 */
public class AvoidReverseTest
{
    public static void main(String[] args) throws UnknownHostException
    {
        long start; InetAddress addr = null; InetSocketAddress sockAddr = null; String dummy = null;

        for(int i=0; i < 3; i++)
        {
            start = System.nanoTime();
            addr = InetAddress.getByName("176.52.246.130");
            sockAddr = new InetSocketAddress(addr, 80);
            dummy = sockAddr.getAddress().getHostName(); dummy.toString();
            System.out.println("byName+getHostName Difference " + ((System.nanoTime() - start) / (1000000.0)) + "ms");
        }
        System.out.println("byName+getHostName: " + dummy);
        System.out.println();

        for(int i=0; i < 3; i++)
        {
            start = System.nanoTime();
            addr = InetAddress.getByName("176.52.246.130");
            sockAddr = new InetSocketAddress(addr, 80);
            dummy = sockAddr.getAddress().toString(); dummy.toString();
            System.out.println("byName+toString Difference " + ((System.nanoTime() - start) / (1000000.0)) + "ms");
        }
        System.out.println("byName+toString: " + dummy);
        System.out.println();

        for(int i=0; i< 3; i++)
        {
            start = System.nanoTime();
            byte[] b = new byte[4]; b[0]=(byte)176; b[1]=(byte)52; b[2]=(byte)246; b[3]=(byte)130;
            addr = InetAddress.getByAddress("176.52.246.130", b);
            sockAddr = new InetSocketAddress(addr, 80);
            dummy = sockAddr.getAddress().getHostName(); dummy.toString();
            System.out.println("byAddress+getHostName Difference " + ((System.nanoTime() - start) / (1000000.0)) + "ms");
        }
        System.out.println("byAddress+getHostName: " + dummy);
        System.out.println();

        for(int i=0; i< 3; i++)
        {
            start = System.nanoTime();
            byte[] b = new byte[4]; b[0]=(byte)176; b[1]=(byte)52; b[2]=(byte)246; b[3]=(byte)130;
            addr = InetAddress.getByAddress("176.52.246.130", b);
            sockAddr = new InetSocketAddress(addr, 80);
            dummy = sockAddr.getAddress().toString(); dummy.toString();
            System.out.println("byAddress+toString Difference " + ((System.nanoTime() - start) / (1000000.0)) + "ms");
        }
        System.out.println("byAddress+toString: " + dummy);

    }

    /* Output:
byName+getHostName Difference 4504.681589ms
byName+getHostName Difference 4499.818737ms
byName+getHostName Difference 4500.038486ms
byName+getHostName: 176.52.246.130

byName+toString Difference 0.088443ms
byName+toString Difference 0.059465ms
byName+toString Difference 0.057352ms
byName+toString: /176.52.246.130

byAddress+getHostName Difference 0.019923ms
byAddress+getHostName Difference 0.006339ms
byAddress+getHostName Difference 0.006339ms
byAddress+getHostName: 176.52.246.130

byAddress+toString Difference 0.025959ms
byAddress+toString Difference 0.022639ms
byAddress+toString Difference 0.022035ms
byAddress+toString: 176.52.246.130/176.52.246.130
    */
}