根据IP地址与字段掩码计算网段最大最小IP
package c04;
import java.net.UnknownHostException;
public class IPNetworkSegmentCalculation {
public static void main(String[] args) throws UnknownHostException {
String ip = "192.168.126.2";
String mask = "255.255.255.0";
findMask();
}
public static void findMask(){
String mask = "255.255.255.0";
String ip = "192.168.126.2";
String[] ipArray = ip.split("[.]");
String[] maskArray = mask.split("[.]");
String minIp = "";
String maxIp = "";
int subMask = 0;
for(int i=0 ;i < maskArray.length ; i++){
int maskTmp = Integer.valueOf(maskArray[i]);
int ipTmp = Integer.valueOf(ipArray[i]);
int mi = maskTmp&ipTmp;
//System.out.println("==============="+maskTmp+" "+ipTmp);
if(ipTmp == mi && maskTmp==255){
minIp = minIp + ipTmp+"." ;
maxIp = maxIp + ipTmp+"." ;
subMask = subMask + 8;
}else{
minIp = minIp + mi+"." ;
maxIp = maxIp + maxNetSeg(Integer.toBinaryString(maskTmp),mi)+".";
subMask = subMask + subMaskNum(Integer.toBinaryString(maskTmp));
}
}
minIp = minIp.substring(0,minIp.length()-1);
maxIp = maxIp.substring(0,maxIp.length()-1);
System.out.println("minip "+minIp);
System.out.println("maxip "+maxIp);
System.out.println("mask "+subMask);
}
private static int calculate(int n) {
if (n == 0)
return 1;
return 2 * calculate(n - 1);
}
private static Integer maxNetSeg(String s1,int mi){
s1 = new StringBuffer(s1).reverse().toString();
if(s1.indexOf("1")!=-1){
int i = s1.indexOf("1");
return mi+calculate(i);
}else {
return 255;
}
}
private static Integer subMaskNum(String s1){
if(s1.lastIndexOf("1")!=-1){
int i = s1.lastIndexOf("1") + 1;
return i;
}
return 0;
}
}
Java根据网段计算子网掩码，起始IP，结束IP
public class IpCaculate {
public static String getNetMask(String maskIndex) {
StringBuilder mask = new StringBuilder();
Integer inetMask = 0;
try {
inetMask = Integer.parseInt(maskIndex);
} catch (NumberFormatException e) {
System.out.println(e.getMessage());
return null;
}
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] += 1 << 8 - num2;
}
for (int i = 0; i < 4; i++) {
if (i == 3) {
mask.append(array[i]);
} else {
mask.append(array[i] + ".");
}
}
return mask.toString();
}
public static String getStartIp(String segment) {
StringBuffer startIp = new StringBuffer();
if (segment == null) {
return null;
}
String arr[] = segment.split("/");
String ip = arr[0];
String maskIndex = arr[1];
String mask = IpCaculate.getNetMask(maskIndex);
if (4 != ip.split("\.").length || mask == null) {
return null;
}
int ipArray[] = new int[4];
int netMaskArray[] = new int[4];
for (int i = 0; i < 4; i++) {
try {
ipArray[i] = Integer.parseInt(ip.split("\.")[i]);
netMaskArray[i] = Integer.parseInt(mask.split("\.")[i]);
if (ipArray[i] > 255 || ipArray[i] < 0 || netMaskArray[i] > 255 || netMaskArray[i] < 0) {
return null;
}
ipArray[i] = ipArray[i] & netMaskArray[i];
if(i==3){
startIp.append(ipArray[i]+1);
}else{
startIp.append(ipArray[i]+".");
}
} catch (NumberFormatException e) {
System.out.println(e.getMessage());
}
}
return startIp.toString();
}
public static String getEndIp(String segment) {
StringBuffer endIp=new StringBuffer();
String startIp = getStartIp(segment);
if (segment == null) {
return null;
}
String arr[] = segment.split("/");
String maskIndex = arr[1];
//实际需要的IP个数
int hostNumber = 0;
int startIpArray[] = new int[4];
try {
hostNumber=1<<32-(Integer.parseInt(maskIndex));
for (int i = 0; i <4; i++) {
startIpArray[i] = Integer.parseInt(startIp.split("\.")[i]);
if(i == 3){
startIpArray[i] = startIpArray[i] - 1;
break;
}
}
startIpArray[3] = startIpArray[3] + (hostNumber - 1);
} catch (NumberFormatException e) {
System.out.println(e.getMessage());
}
if(startIpArray[3] >255){
int k = startIpArray[3] / 256;
startIpArray[3] = startIpArray[3] % 256;
startIpArray[2] = startIpArray[2] + k;
}
if(startIpArray[2] > 255){
int j = startIpArray[2] / 256;
startIpArray[2] = startIpArray[2] % 256;
startIpArray[1] = startIpArray[1] + j;
if(startIpArray[1] > 255){
int k = startIpArray[1] / 256;
startIpArray[1] = startIpArray[1] % 256;
startIpArray[0] = startIpArray[0] + k;
}
}
for(int i = 0; i < 4; i++){
if(i == 3){
startIpArray[i] = startIpArray[i] - 1;
}
if("" == endIp.toString()||endIp.length()==0){
endIp.append(startIpArray[i]);
}else{
endIp.append("." + startIpArray[i]);
}
}
return endIp.toString();
}
}
根据网段计算起始IP 网段格式:x.x.x.x/x
网段内需要的IP数量为：2的（32-掩码位）次方个。
因为一个网段0一般为网络地址,255一般为广播地址， 所以第一个可用IP起始IP计算:网段与掩码相与之后加一的IP地址，结束IP为通过计算需要的所有IP数然后做累加运算，超过256则进位进行运算。
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