Java IP Address Get getLocalIp()

Description

get Local Ip

License

Open Source License

Declaration

public static String getLocalIp() 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

import java.net.InetAddress;
import java.net.NetworkInterface;

import java.util.Enumeration;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Main {
    public static String getLocalIp(String ipPreference) {
        if (ipPreference == null) {
            ipPreference = "*>10>172>192>127";
        }//from   w  w w  . j a  va 2s  .  c o  m
        String[] prefix = ipPreference.split("[> ]+");
        try {
            Pattern pattern = Pattern.compile("[0-9]+\\.[0-9]+\\.[0-9]+\\.[0-9]+");
            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
            String matchedIp = null;
            int matchedIdx = -1;
            while (interfaces.hasMoreElements()) {
                NetworkInterface ni = interfaces.nextElement();
                Enumeration<InetAddress> en = ni.getInetAddresses();
                while (en.hasMoreElements()) {
                    InetAddress addr = en.nextElement();
                    String ip = addr.getHostAddress();
                    Matcher matcher = pattern.matcher(ip);
                    if (matcher.matches()) {
                        int idx = matchedIndex(ip, prefix);
                        if (idx == -1)
                            continue;
                        if (matchedIdx == -1) {
                            matchedIdx = idx;
                            matchedIp = ip;
                        } else {
                            if (matchedIdx > idx) {
                                matchedIdx = idx;
                                matchedIp = ip;
                            }
                        }
                    }
                }
            }
            if (matchedIp != null)
                return matchedIp;
            return "127.0.0.1";
        } catch (Throwable e) {
            return "127.0.0.1";
        }
    }

    public static String getLocalIp() {
        return getLocalIp("*>10>172>192>127");
    }

    private static int matchedIndex(String ip, String[] prefix) {
        for (int i = 0; i < prefix.length; i++) {
            String p = prefix[i];
            if ("*".equals(p)) { //*, assumed to be IP
                if (ip.startsWith("127.") || ip.startsWith("10.") || ip.startsWith("172.")
                        || ip.startsWith("192.")) {
                    continue;
                }
                return i;
            } else {
                if (ip.startsWith(p)) {
                    return i;
                }
            }
        }

        return -1;
    }
}

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