IP

127.0.0.1 本机： localhost

ip地址分类：
ipv4/ipv6

ipv4 例： 127.0.0.1 4个字节组成 0-255
ipv6 例： 2409:8a62:efc:bf70:f809:4c01:8c86:e78 128位 8个无符号整数！

公网（互联网）/私网（局域网）
192.168.xx.xx 专门给组织内部使用的
域名：记忆IP问题！

TestInetAddress

package com.guo.lesson01;

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

//测试 IP
public class TestInetAddress {
    public static void main(String[] args) {
        try {

            //查询本机地址
            InetAddress inetAddress1 = InetAddress.getByName("127.0.0.1");
            System.out.println(inetAddress1);
            InetAddress inetAddress3 = InetAddress.getByName("localhost");
            System.out.println(inetAddress3);
            InetAddress inetAddress4 = InetAddress.getLocalHost();
            System.out.println(inetAddress4);

            //查询网站ip地址
            InetAddress inetAddress2 = InetAddress.getByName("www.baidu.com");
            System.out.println(inetAddress2);

            //常用方法
            //System.out.println(inetAddress2.getAddress());
            System.out.println(inetAddress2.getCanonicalHostName());//规范的名字
            System.out.println(inetAddress2.getHostAddress());//ip
            System.out.println(inetAddress2.getHostName());//域名，或者自己电脑的名字

        } catch (UnknownHostException e) {
            throw new RuntimeException(e);
        }
    }
}