在Java中，可以使用InetAddress類來獲取IP地址。

以下是一些示例代碼：

1. 獲取本機IP地址：

import java.net.InetAddress;

public class Main {
    public static void main(String[] args) {
        try {
            InetAddress localhost = InetAddress.getLocalHost();
            System.out.println("本機IP地址: " + localhost.getHostAddress());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

2. 獲取指定域名的IP地址：

import java.net.InetAddress;

public class Main {
    public static void main(String[] args) {
        try {
            InetAddress address = InetAddress.getByName("www.google.com");
            System.out.println("www.google.com 的IP地址: " + address.getHostAddress());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

注意：InetAddress.getLocalHost()方法可能返回本機的IPv6地址，而不是IPv4地址。如果需要獲取IPv4地址，可以使用NetworkInterface類來獲取本機的網絡接口，然后從中獲取IPv4地址。

例如：

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.util.Enumeration;

public class Main {
    public static void main(String[] args) {
        try {
            Enumeration<NetworkInterface> interfaces = NetworkInterface.getNetworkInterfaces();
            while (interfaces.hasMoreElements()) {
                NetworkInterface networkInterface = interfaces.nextElement();
                Enumeration<InetAddress> addresses = networkInterface.getInetAddresses();
                while (addresses.hasMoreElements()) {
                    InetAddress address = addresses.nextElement();
                    if (!address.isLoopbackAddress() && address.getHostAddress().indexOf(":") == -1) {
                        System.out.println("本機IPv4地址: " + address.getHostAddress());
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}