Java 实现ip 转 cidr

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自己工作需要，实现ip转cidr
看到网上有人实现，拿来自己用了
    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();               }       }
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