Created
July 23, 2012 15:48
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Parsing an IP Address in Java
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public static InetAddress parseIpAddress(String ip) throws IllegalArgumentException { | |
StringTokenizer tok = new StringTokenizer(ip, "."); | |
if (tok.countTokens() != 4) { | |
throw new IllegalArgumentException("IP address must be in the format 'xxx.xxx.xxx.xxx'"); | |
} | |
byte[] data = new byte[4]; | |
int i = 0; | |
while (tok.hasMoreTokens()) { | |
String strVal = tok.nextToken(); | |
try { | |
int val = Integer.parseInt(tok.nextToken(), 10); | |
if (val < 0 || val > 255) { | |
throw new IllegalArgumentException("Illegal value '" + val + "' at byte " + (i + 1) + " in the IP address."); | |
} | |
data[i++] = (byte) Integer.parseInt(tok.nextToken(), 10); | |
} catch (NumberFormatException e) { | |
throw new IllegalArgumentException("Illegal value '" + strVal + "' at token " + (i + 1) + " in the IP address.", e); | |
} | |
} | |
try { | |
return InetAddress.getByAddress(ip, data); | |
} catch (UnknownHostException e) { | |
// This actually can't happen since the method InetAddress.getByAddress(String, byte[]) | |
// doesn't perform any lookups and we have already guaranteed that the length of data is 4 | |
throw new Error("UnknownHostException somehow thrown when creating an InetAddress", e); | |
} | |
} |
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inside
while()
loop, on lines 13 and 19, changetok.nextToken()
tostrVal