2.通过域名获取ip，通过ip获取域名

1）核心代码

public static void main(String[] args) throws UnknownHostException {
    
    
    //通过域名获得ip地址
    String domain="www.baidu.com";
    InetAddress inetAddr=InetAddress.getByName(domain);
    System.out.println(domain+"对应ip为："+inetAddr.getHostAddress());

    //通过ip地址获得域名
    System.out.println(getCanonicalNameByIp("127.0.0.1"));
}

/**
 * 通过ip获得域名
 * @param ip
 * @return
 * @throws UnknownHostException
 */
public static String getCanonicalNameByIp(String ip) throws UnknownHostException {
    
    
    String[] ipStr=ip.split("[.]");
    byte[] ipBytes=new byte[4];
    for(int i=0;i<4;i++){
    
    
        int m=Integer.parseInt(ipStr[i]);
        ipBytes[i]=(byte)(m&0xff);
    }
    InetAddress inetAddressByIp=InetAddress.getByAddress(ipBytes);
    return inetAddressByIp.getCanonicalHostName();
}