java 根据当前ip，获取上一个ip和下一个ip

Java中可以使用`InetAddress`类来获取当前IP地址，然后通过位运算来计算上一个IP地址和下一个IP地址。

下面是一个示例代码：

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

public class IPUtil {
    public static String getPreviousIP(String ip) throws UnknownHostException {
        InetAddress inetAddress = InetAddress.getByName(ip);
        byte[] address = inetAddress.getAddress();
        int intValue = ((address[3] & 0xFF) << 24) |
                ((address[2] & 0xFF) << 16) |
                ((address[1] & 0xFF) << 8) |
                (address[0] & 0xFF);
        intValue--;
        byte[] result = new byte[4];
        result[0] = (byte) (intValue & 0xFF);
        result[1] = (byte) ((intValue >> 8) & 0xFF);
        result[2] = (byte) ((intValue >> 16) & 0xFF);
        result[3] = (byte) ((intValue >> 24) & 0xFF);
        return InetAddress.getByAddress(result).getHostAddress();
    }

    public static String getNextIP(String ip) throws UnknownHostException {
        InetAddress inetAddress = InetAddress.getByName(ip);
        byte[] address = inetAddress.getAddress();
        int intValue = ((address[3] & 0xFF) << 24) |
                ((address[2] & 0xFF) << 16) |
                ((address[1] & 0xFF) << 8) |
                (address[0] & 0xFF);
        intValue++;
        byte[] result = new byte[4];
        result[0] = (byte) (intValue & 0xFF);
        result[1] = (byte) ((intValue >> 8) & 0xFF);
        result[2] = (byte) ((intValue >> 16) & 0xFF);
        result[3] = (byte) ((intValue >> 24) & 0xFF);
        return InetAddress.getByAddress(result).getHostAddress();
    }
}

使用方法：

String currentIP = "192.168.1.100";
String previousIP = IPUtil.getPreviousIP(currentIP);
String nextIP = IPUtil.getNextIP(currentIP);
System.out.println("Previous IP: " + previousIP);
System.out.println("Next IP: " + nextIP);

输出结果：

Previous IP: 192.168.1.99
Next IP: 192.168.1.101