如果您的机器是网络的一部分，那么它将获取您的网络的IP地址

try {
    System.out.println(InetAddress.getLocalHost().getHostAddress());
} catch (UnknownHostException e) {
    e.printStackTrace();
}

通常当我试图找到我的公共IP地址，如cmyip.com或www.iplocation.net，我使用这种方式:

public static String myPublicIp() {

    /*nslookup myip.opendns.com resolver1.opendns.com*/
    String ipAdressDns  = "";
    try {
        String command = "nslookup myip.opendns.com resolver1.opendns.com";
        Process proc = Runtime.getRuntime().exec(command);

        BufferedReader stdInput = new BufferedReader(new InputStreamReader(proc.getInputStream()));

        String s;
        while ((s = stdInput.readLine()) != null) {
            ipAdressDns  += s + "\n";
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    return ipAdressDns ;
}

scala中的示例(在sbt文件中有用):

  import collection.JavaConverters._
  import java.net._

  def getIpAddress: String = {

    val enumeration = NetworkInterface.getNetworkInterfaces.asScala.toSeq

    val ipAddresses = enumeration.flatMap(p =>
      p.getInetAddresses.asScala.toSeq
    )

    val address = ipAddresses.find { address =>
      val host = address.getHostAddress
      host.contains(".") && !address.isLoopbackAddress
    }.getOrElse(InetAddress.getLocalHost)

    address.getHostAddress
  }

在这里发布来自https://issues.apache.org/jira/browse/JCS-40的测试IP歧义变通代码(InetAddress.getLocalHost()在Linux系统上是歧义的):

/**
 * Returns an <code>InetAddress</code> object encapsulating what is most likely the machine's LAN IP address.
 * <p/>
 * This method is intended for use as a replacement of JDK method <code>InetAddress.getLocalHost</code>, because
 * that method is ambiguous on Linux systems. Linux systems enumerate the loopback network interface the same
 * way as regular LAN network interfaces, but the JDK <code>InetAddress.getLocalHost</code> method does not
 * specify the algorithm used to select the address returned under such circumstances, and will often return the
 * loopback address, which is not valid for network communication. Details
 * <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4665037">here</a>.
 * <p/>
 * This method will scan all IP addresses on all network interfaces on the host machine to determine the IP address
 * most likely to be the machine's LAN address. If the machine has multiple IP addresses, this method will prefer
 * a site-local IP address (e.g. 192.168.x.x or 10.10.x.x, usually IPv4) if the machine has one (and will return the
 * first site-local address if the machine has more than one), but if the machine does not hold a site-local
 * address, this method will return simply the first non-loopback address found (IPv4 or IPv6).
 * <p/>
 * If this method cannot find a non-loopback address using this selection algorithm, it will fall back to
 * calling and returning the result of JDK method <code>InetAddress.getLocalHost</code>.
 * <p/>
 *
 * @throws UnknownHostException If the LAN address of the machine cannot be found.
 */
private static InetAddress getLocalHostLANAddress() throws UnknownHostException {
    try {
        InetAddress candidateAddress = null;
        // Iterate all NICs (network interface cards)...
        for (Enumeration ifaces = NetworkInterface.getNetworkInterfaces(); ifaces.hasMoreElements();) {
            NetworkInterface iface = (NetworkInterface) ifaces.nextElement();
            // Iterate all IP addresses assigned to each card...
            for (Enumeration inetAddrs = iface.getInetAddresses(); inetAddrs.hasMoreElements();) {
                InetAddress inetAddr = (InetAddress) inetAddrs.nextElement();
                if (!inetAddr.isLoopbackAddress()) {

                    if (inetAddr.isSiteLocalAddress()) {
                        // Found non-loopback site-local address. Return it immediately...
                        return inetAddr;
                    }
                    else if (candidateAddress == null) {
                        // Found non-loopback address, but not necessarily site-local.
                        // Store it as a candidate to be returned if site-local address is not subsequently found...
                        candidateAddress = inetAddr;
                        // Note that we don't repeatedly assign non-loopback non-site-local addresses as candidates,
                        // only the first. For subsequent iterations, candidate will be non-null.
                    }
                }
            }
        }
        if (candidateAddress != null) {
            // We did not find a site-local address, but we found some other non-loopback address.
            // Server might have a non-site-local address assigned to its NIC (or it might be running
            // IPv6 which deprecates the "site-local" concept).
            // Return this non-loopback candidate address...
            return candidateAddress;
        }
        // At this point, we did not find a non-loopback address.
        // Fall back to returning whatever InetAddress.getLocalHost() returns...
        InetAddress jdkSuppliedAddress = InetAddress.getLocalHost();
        if (jdkSuppliedAddress == null) {
            throw new UnknownHostException("The JDK InetAddress.getLocalHost() method unexpectedly returned null.");
        }
        return jdkSuppliedAddress;
    }
    catch (Exception e) {
        UnknownHostException unknownHostException = new UnknownHostException("Failed to determine LAN address: " + e);
        unknownHostException.initCause(e);
        throw unknownHostException;
    }
}

编辑1:更新后的代码，因为之前的链接，不再存在

import java.io.*;
import java.net.*;

public class GetMyIP {
    public static void main(String[] args) {
        URL url = null;
        BufferedReader in = null;
        String ipAddress = "";
        try {
            url = new URL("http://bot.whatismyipaddress.com");
            in = new BufferedReader(new InputStreamReader(url.openStream()));
            ipAddress = in.readLine().trim();
            /* IF not connected to internet, then
             * the above code will return one empty
             * String, we can check it's length and
             * if length is not greater than zero, 
             * then we can go for LAN IP or Local IP
             * or PRIVATE IP
             */
            if (!(ipAddress.length() > 0)) {
                try {
                    InetAddress ip = InetAddress.getLocalHost();
                    System.out.println((ip.getHostAddress()).trim());
                    ipAddress = (ip.getHostAddress()).trim();
                } catch(Exception exp) {
                    ipAddress = "ERROR";
                }
            }
        } catch (Exception ex) {
            // This try will give the Private IP of the Host.
            try {
                InetAddress ip = InetAddress.getLocalHost();
                System.out.println((ip.getHostAddress()).trim());
                ipAddress = (ip.getHostAddress()).trim();
            } catch(Exception exp) {
                ipAddress = "ERROR";
            }
            //ex.printStackTrace();
        }
        System.out.println("IP Address: " + ipAddress);
    }
}

实际版本:这停止工作

希望这段代码可以帮助你实现这一点:

// Method to get the IP Address of the Host.
private String getIP()
{
    // This try will give the Public IP Address of the Host.
    try
    {
        URL url = new URL("http://automation.whatismyip.com/n09230945.asp");
        BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
        String ipAddress = new String();
        ipAddress = (in.readLine()).trim();
        /* IF not connected to internet, then
         * the above code will return one empty
         * String, we can check it's length and
         * if length is not greater than zero, 
         * then we can go for LAN IP or Local IP
         * or PRIVATE IP
         */
        if (!(ipAddress.length() > 0))
        {
            try
            {
                InetAddress ip = InetAddress.getLocalHost();
                System.out.println((ip.getHostAddress()).trim());
                return ((ip.getHostAddress()).trim());
            }
            catch(Exception ex)
            {
                return "ERROR";
            }
        }
        System.out.println("IP Address is : " + ipAddress);

        return (ipAddress);
    }
    catch(Exception e)
    {
        // This try will give the Private IP of the Host.
        try
        {
            InetAddress ip = InetAddress.getLocalHost();
            System.out.println((ip.getHostAddress()).trim());
            return ((ip.getHostAddress()).trim());
        }
        catch(Exception ex)
        {
            return "ERROR";
        }
    }
}

在大多数情况下，这可能有点棘手。

从表面上看，InetAddress.getLocalHost()应该提供该主机的IP地址。问题是一台主机可能有很多网络接口，而一个接口可能绑定到多个IP地址。最重要的是，并不是所有的IP地址都可以在您的机器或局域网之外访问。例如，它们可以是虚拟网络设备的IP地址、私有网络IP地址等等。

这意味着InetAddress.getLocalHost()返回的IP地址可能不是要使用的正确IP地址。

你怎么处理这个问题呢?

One approach is to use NetworkInterface.getNetworkInterfaces() to get all of the known network interfaces on the host, and then iterate over each NI's addresses. Another approach is to (somehow) get the externally advertized FQDN for the host, and use InetAddress.getByName() to look up the primary IP address. (But how do you get it, and how do you deal with a DNS-based load balancer?) A variation of the previous is to get the preferred FQDN from a config file or a command line parameter. Another variation is to get the preferred IP address from a config file or a command line parameter.

总之，InetAddress.getLocalHost()通常可以工作，但是对于代码运行在“复杂”网络环境中的情况，您可能需要提供另一种方法。

我能够获得所有网络接口相关的所有IP地址，但我如何区分它们?

Any address in the range 127.xxx.xxx.xxx is a "loopback" address. It is only visible to "this" host. Any address in the range 192.168.xxx.xxx is a private (aka site local) IP address. These are reserved for use within an organization. The same applies to 10.xxx.xxx.xxx addresses, and 172.16.xxx.xxx through 172.31.xxx.xxx. Addresses in the range 169.254.xxx.xxx are link local IP addresses. These are reserved for use on a single network segment. Addresses in the range 224.xxx.xxx.xxx through 239.xxx.xxx.xxx are multicast addresses. The address 255.255.255.255 is the broadcast address. Anything else should be a valid public point-to-point IPv4 address.

事实上，InetAddress API提供了测试环回、链路本地、站点本地、组播和广播地址的方法。您可以使用这些来分类您获得的哪个IP地址是最合适的。