Here you can find the source of getHostName()
public static String getHostName() throws UnknownHostException
//package com.java2s; /**//w w w .j a v a 2 s . co m * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you under the Apache License, Version 2.0 (the * "License"); you may not use this file except in compliance * with the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ import java.net.*; public class Main { private static InetAddress localInetAddress_; public static String getHostName() throws UnknownHostException { return getLocalAddress().getCanonicalHostName(); } public static InetAddress getLocalAddress() throws UnknownHostException { if (localInetAddress_ == null) localInetAddress_ = InetAddress.getLocalHost(); return localInetAddress_; } }