Java – Convert IP address to Decimal Number
2016-07-17 17:50
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In this tutorial, we show you how to convert an IP address to its decimal equivalent in Java, and vice versa. For examples :
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Normal power of 256
Bit shifting
1.1 First Example – Power of 256
The IP address is “base 256”, to convert
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Java
Some developers prefer to use modular like this
Java
1.2 Second Example - Bit shifting
Review the binary bit shifting graph below :
Java
Bash
Convert the final binary code to decimal, by hand calculation :) ~
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2.1 First Example.
Java
Review the bit shifting flows :
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2.2 Second Example.
Java
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Java
Output
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地址:http://www.mkyong.com/java/java-convert-ip-address-to-decimal-number/[/code]
Bash
255.255.255.255 <-> 4294967295 192.168.1.2 <-> 3232235778
1. IP Address to Decimal
We show you two ways to convert an IP address to a decimal numberNormal power of 256
Bit shifting
1.1 First Example – Power of 256
The IP address is “base 256”, to convert
192.168.1.2to decimal (base 10) the formula is:
Bash
192 x (256)^3 + 168 x (256)^2 + 1 x (256)^1 + 2 (256)^0 = ? 3221225472 + 11010048 + 256 + 2 = 3232235778
Java
public long ipToLong(String ipAddress) { String[] ipAddressInArray = ipAddress.split("\\."); long result = 0; for (int i = 0; i < ipAddressInArray.length; i++) { int power = 3 - i; int ip = Integer.parseInt(ipAddressInArray[i]); result += ip * Math.pow(256, power); } return result; }
Some developers prefer to use modular like this
Java
result += (Integer.parseInt(ipAddressInArray[i]) % 256 * Math.pow(256, power));
1.2 Second Example - Bit shifting
Review the binary bit shifting graph below :
Java
public long ipToLong(String ipAddress) { long result = 0; String[] ipAddressInArray = ipAddress.split("\\."); for (int i = 3; i >= 0; i--) { long ip = Long.parseLong(ipAddressInArray[3 - i]); //left shifting 24,16,8,0 and bitwise OR //1. 192 << 24 //1. 168 << 16 //1. 1 << 8 //1. 2 << 0 result |= ip << (i * 8); } return result; }
Bash
192 00000000 00000000 00000000 11000000 ----------------------------------------------- 192 << 24 11000000 00000000 00000000 00000000 Result 00000000 00000000 00000000 00000000 Result |= 11000000 00000000 00000000 00000000 168 00000000 00000000 00000000 10101000 ----------------------------------------------- 168 << 16 00000000 10101000 00000000 00000000 Result 11000000 00000000 00000000 00000000 Result |= 11000000 10101000 00000000 00000000 1 00000000 00000000 00000000 00000001 ----------------------------------------------- 1 << 8 00000000 00000000 00000001 00000000 Result 11000000 10101000 00000000 00000000 Result |= 11000000 10101000 00000001 00000000 2 00000000 00000000 00000000 00000010 ----------------------------------------------- 2 << 0 00000000 00000000 00000000 00000010 Result 11000000 10101000 00000001 00000000 Result |= 11000000 10101000 00000001 00000010
Convert the final binary code to decimal, by hand calculation :) ~
Bash
Result 11000000 10101000 00000001 00000010 index 0 - 31, start from right. 31(1),30(1),29,28,27,26,25,24,23(1),22,21(1),20,19(1),18,17,16,15,14,13,12,11,10,9,8(1),7,6,5,4,3,2,1(1),0 Decimal 1x2^31 + 1x2^30 + 1x2^23 + 1x2^21 + 1x2^19 + 1x2^8 + 1x2^1 2147483648 + 1073741824 + 8388608 + 2097152 + 524288 + 256 + 2 3232235778
2. Decimal to IP Address
We show you two bit shifting and "0xff" masking examples to convert a decimal number back to IP address. The bit shifting is very hard to explain in words, it's better review the binary flows below :2.1 First Example.
Java
//ip = 3232235778 public String longToIp(long ip) { StringBuilder result = new StringBuilder(15); for (int i = 0; i < 4; i++) { result.insert(0,Long.toString(ip & 0xff)); if (i < 3) { sb.insert(0,'.'); } ip = ip >> 8; } return result.toString(); }
Review the bit shifting flows :
Bash
3232235778 11000000 10101000 00000001 00000010 <<Loop 1>> ----------------------------------------------------------- ip 11000000 10101000 00000001 00000010 & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 00000010 = 2 Result Append .2 -------------------------> 8 ip >> 8 00000000 11000000 10101000 00000001 {off 00000010} <<Loop 2>> ----------------------------------------------------------- ip 00000000 11000000 10101000 00000001 & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 00000001 = 1 Result Append 1.2 ----------------> 8 ip >> 8 00000000 00000000 11000000 10101000 {off 00000001} <<Loop 3>> ----------------------------------------------------------- ip 00000000 00000000 11000000 10101000 & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 10101000 = 168 Result Append 168.1.2 -------> 8 ip >> 8 00000000 00000000 00000000 11000000 {off 10101000} <<Loop 4>> ----------------------------------------------------------- ip 00000000 00000000 00000000 11000000 & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 11000000 = 192 Result Append 192.168.1.2 -----------> 8 ip >> 8 00000000 00000000 00000000 00000000 {off 11000000}
2.2 Second Example.
Java
//ip = 3232235778 public String longToIp(long ip) { return ((ip >> 24) & 0xFF) + "." + ((ip >> 16) & 0xFF) + "." + ((ip >> 8) & 0xFF) + "." + (ip & 0xFF); }
Bash
3232235778 11000000 10101000 00000001 00000010 1. (ip >> 24) & 0xFF ----------------------------------------------------------- ip 11000000 10101000 00000001 00000010 -------------------------------------> 24 ip >> 24 00000000 00000000 00000000 11000000 {off 10101000 00000001 00000010} & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 11000000 = 192 2. (ip >> 16) & 0xFF ----------------------------------------------------------- ip 11000000 10101000 00000001 00000010 -------------------------------------> 16 ip >> 16 00000000 00000000 11000000 10101000 {off 00000001 00000010} & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 10101000 = 168 3. (ip >> 8) & 0xFF ----------------------------------------------------------- ip 11000000 10101000 00000001 00000010 --------------------------------------> 8 ip >> 24 00000000 11000000 10101000 00000001 {off 00000010} & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 00000001 = 1 4. ip & 0xFF ----------------------------------------------------------- ip 11000000 10101000 00000001 00000010 & 0xff 00000000 00000000 00000000 11111111 Result 00000000 00000000 00000000 00000010 = 2
3. Java Source Code
Full Java example to demonstrate above scenario :Java
package com.mkyong.core; public class JavaBitwiseExample { public static void main(String[] args) { JavaBitwiseExample obj = new JavaBitwiseExample(); System.out.println("iptoLong : " + obj.ipToLong("192.168.1.2")); System.out.println("iptoLong2 : " + obj.ipToLong2("192.168.1.2")); System.out.println("longToIp : " + obj.longToIp(3232235778L)); System.out.println("longToIp2 : " + obj.longToIp2(3232235778L)); } // example : 192.168.1.2 public long ipToLong(String ipAddress) { // ipAddressInArray[0] = 192 String[] ipAddressInArray = ipAddress.split("\\."); long result = 0; for (int i = 0; i < ipAddressInArray.length; i++) { int power = 3 - i; int ip = Integer.parseInt(ipAddressInArray[i]); // 1. 192 * 256^3 // 2. 168 * 256^2 // 3. 1 * 256^1 // 4. 2 * 256^0 result += ip * Math.pow(256, power); } return result; } public long ipToLong2(String ipAddress) { long result = 0; String[] ipAddressInArray = ipAddress.split("\\."); for (int i = 3; i >= 0; i--) { long ip = Long.parseLong(ipAddressInArray[3 - i]); // left shifting 24,16,8,0 and bitwise OR // 1. 192 << 24 // 1. 168 << 16 // 1. 1 << 8 // 1. 2 << 0 result |= ip << (i * 8); } return result; } public String longToIp(long i) { return ((i >> 24) & 0xFF) + "." + ((i >> 16) & 0xFF) + "." + ((i >> 8) & 0xFF) + "." + (i & 0xFF); } public String longToIp2(long ip) { StringBuilder sb = new StringBuilder(15); for (int i = 0; i < 4; i++) { // 1. 2 // 2. 1 // 3. 168 // 4. 192 sb.insert(0, Long.toString(ip & 0xff)); if (i < 3) { sb.insert(0, '.'); } // 1. 192.168.1.2 // 2. 192.168.1 // 3. 192.168 // 4. 192 ip = ip >> 8; } return sb.toString(); } /* private static void printPrettyBinary(String binary) { String s1 = String.format("%32s", binary).replace(' ', '0'); System.out.format("%8s %8s %8s %8s %n", s1.substring(0, 8), s1.substring(8, 16), s1.substring(16, 24), s1.substring(24, 32)); } */ }
Output
Bash
iptoLong : 3232235778 iptoLong2 : 3232235778 longToIp : 192.168.1.2 longToIp2 : 192.168.1.2
地址:http://www.mkyong.com/java/java-convert-ip-address-to-decimal-number/[/code]
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