10.计算IP和子网掩码

public class T3 {
public static void main(String[] args) {
String cidr = "132.147.123.0/24";
String mask = cidr.substring(cidr.indexOf("/") + 1);
System.out.println(mask);
String ipInfo = cidr.substring(0, cidr.indexOf("/"));
System.out.println(ipInfo);
System.out.println(ipInfo.split("\.").length);
System.out.println(getSubnetMask(mask));
System.out.println(getStartAddr(ipInfo, getSubnetMask(mask)));
System.out.println(getEndAddr(ipInfo, getSubnetMask(mask)));
System.out.println(getHostNumber(getSubnetMask(mask)));
}

/**
 * 计算子网掩码
 * 
 * @param inMask
 * @return
 */
public static String getSubnetMask(String inMask) {
	int inetMask = Integer.parseInt(inMask);
	if (inetMask > 32) {
		return null;
	}
	// 子网掩码为1占了几个字节
	int num1 = inetMask / 8;
	// 子网掩码的补位位数
	int num2 = inetMask % 8;
	int array[] = new int[4];
	for (int i = 0; i < num1; i++) {
		array[i] = 255;
	}
	for (int i = num1; i < 4; i++) {
		array[i] = 0;
	}
	for (int i = 0; i < num2; num2--) {
		array[num1] += Math.pow(2, 8 - num2);
	}
	String netMask = array[0] + "." + array[1] + "." + array[2] + "." + array[3];
	return netMask;
}

/**
 * 获取子网下的起始IP的地址
 * 
 * @param ipInfo
 * @param netMask
 * @return
 */
public static String getStartAddr(String ipInfo, String netMask) {
	String lowAddr = "";
	int ipArray[] = new int[4];
	int netMaskArray[] = new int[4];
	if (4 != ipInfo.split("\\.").length || "" == netMask) {
		return null;
	}
	for (int i = 0; i < 4; i++) {
		try {
			ipArray[i] = Integer.parseInt(ipInfo.split("\\.")[i]);
		} catch (NumberFormatException e) {
			String ip = ipInfo.replaceAll("\n", "");
			ipArray[i] = Integer.parseInt(ip.split("\\.")[i]);
		}
		netMaskArray[i] = Integer.parseInt(netMask.split("\\.")[i]);
		if (ipArray[i] > 255 || ipArray[i] < 0 || netMaskArray[i] > 255 || netMaskArray[i] < 0) {
			return null;
		}
		ipArray[i] = ipArray[i] & netMaskArray[i];
	}
	// 构造最小地址
	for (int i = 0; i < 4; i++) {
		if (i == 3) {
			ipArray[i] = ipArray[i] + 1;
		}
		if ("" == lowAddr) {
			lowAddr += ipArray[i];
		} else {
			lowAddr += "." + ipArray[i];
		}
	}
	return lowAddr;
}

/**
 * 获取子网下的结束Ip地址
 * 
 * @param ipInfo
 * @param netMask
 * @return
 */
public static String getEndAddr(String ipInfo, String netMask) {
	String lowAddr = getStartAddr(ipInfo, netMask);
	int hostNumber = getHostNumber(netMask);
	if ("" == lowAddr || hostNumber == 0) {
		return null;
	}
	int lowAddrArray[] = new int[4];
	for (int i = 0; i < 4; i++) {
		lowAddrArray[i] = Integer.parseInt(lowAddr.split("\\.")[i]);
		if (i == 3) {
			lowAddrArray[i] = lowAddrArray[i] - 1;
		}
	}
	lowAddrArray[3] = lowAddrArray[3] + (hostNumber - 1);
	if (lowAddrArray[3] > 255) {
		int k = lowAddrArray[3] / 256;
		lowAddrArray[3] = lowAddrArray[3] % 256;
		lowAddrArray[2] = lowAddrArray[2] + k;
	}
	if (lowAddrArray[2] > 255) {
		int j = lowAddrArray[2] / 256;
		lowAddrArray[2] = lowAddrArray[2] % 256;
		lowAddrArray[1] = lowAddrArray[1] + j;
		if (lowAddrArray[1] > 255) {
			int k = lowAddrArray[1] / 256;
			lowAddrArray[1] = lowAddrArray[1] % 256;
			lowAddrArray[0] = lowAddrArray[0] + k;
		}
	}
	String highAddr = "";
	for (int i = 0; i < 4; i++) {
		if (i == 3) {
			lowAddrArray[i] = lowAddrArray[i] - 1;
		}
		if ("" == highAddr) {
			highAddr = lowAddrArray[i] + "";
		} else {
			highAddr += "." + lowAddrArray[i];
		}
	}
	return highAddr;
}

/**
 * 实际可用IP数量,包括0和255.必须减去2
 * 
 * @param netMask
 * @return
 */
public static int getHostNumber(String netMask) {
	int hostNumber = 0;
	int netMaskArray[] = new int[4];
	for (int i = 0; i < 4; i++) {
		netMaskArray[i] = Integer.parseInt(netMask.split("\\.")[i]);
		if (netMaskArray[i] < 255) {
			hostNumber = (int) (Math.pow(256, 3 - i) * (256 - netMaskArray[i]));
			break;
		}
	}
	return hostNumber;
}

/**
 * ip转换为long
 * 
 * @param ip
 * @return
 */
private long ip2long(String ip) {
	String[] ips = ip.split("[.]");
	long num = 16777216L * Long.parseLong(ips[0]) + 65536L * Long.parseLong(ips[1]) + 256 * Long.parseLong(ips[2])
			+ Long.parseLong(ips[3]);
	return num;
}

}