我的最后一个答案中包含一些错误，这些错误是由于IP地址的第一个八位字节太大而引起的。这个效果更好。几乎完全从这里解除：http : //facedroid.blogspot.com/2010/06/ip-range-to-
cidr.html
import java.util.ArrayList;import java.util.List;public class RangeToCidr { public static List<String> range2cidrlist( String startIp, String endIp ) { long start = ipToLong(startIp); long end = ipToLong(endIp); ArrayList<String> pairs = new ArrayList<String>(); while ( end >= start ) { byte maxsize = 32; while ( maxsize > 0) {long mask = CIDR2MASK[ maxsize -1 ];long maskedbase = start & mask; if ( maskedbase != start ) { break;} maxsize--; } double x = Math.log( end - start + 1) / Math.log( 2 ); byte maxdiff = (byte)( 32 - Math.floor( x ) ); if ( maxsize < maxdiff) {maxsize = maxdiff; } String ip = longToIP(start); pairs.add( ip + "/" + maxsize); start += Math.pow( 2, (32 - maxsize) ); } return pairs; } public static final int[] CIDR2MASK = new int[] { 0x00000000, 0x80000000, 0xC0000000, 0xE0000000, 0xF0000000, 0xF8000000, 0xFC000000, 0xFE000000, 0xFF000000, 0xFF800000, 0xFFC00000, 0xFFE00000, 0xFFF00000, 0xFFF80000, 0xFFFC0000, 0xFFFE0000, 0xFFFF0000, 0xFFFF8000, 0xFFFFC000, 0xFFFFE000, 0xFFFFF000, 0xFFFFF800, 0xFFFFFC00, 0xFFFFFE00, 0xFFFFFF00, 0xFFFFFF80, 0xFFFFFFC0, 0xFFFFFFE0, 0xFFFFFFF0, 0xFFFFFFF8, 0xFFFFFFFC, 0xFFFFFFFE, 0xFFFFFFFF }; private static long ipToLong(String strIP) { long[] ip = new long[4]; String[] ipSec = strIP.split("\."); for (int k = 0; k < 4; k++) { ip[k] = Long.valueOf(ipSec[k]); } return (ip[0] << 24) + (ip[1] << 16) + (ip[2] << 8) + ip[3]; } private static String longToIP(long longIP) { StringBuffer sb = new StringBuffer(""); sb.append(String.valueOf(longIP >>> 24)); sb.append("."); sb.append(String.valueOf((longIP & 0x00FFFFFF) >>> 16)); sb.append("."); sb.append(String.valueOf((longIP & 0x0000FFFF) >>> 8)); sb.append("."); sb.append(String.valueOf(longIP & 0x000000FF)); return sb.toString(); } }
