Remove IP addresses from a String in Java

Question

Is there any way that you can remove IPs from a string?

The input file we get sometimes has IPs attached to the user name, e.g.

Jan vd Merwe
Piet Breedt (172.166.23.41)
Jan vd Merwe (164.23.23.51)
Sarel Fourie (23.12.167.244)
Piet Breedt

So if there is an IP, I want to remove it. I have been looking at alot of functions but cant seem to get the indexing and parameters right.

Do you like to extract the ip? (Or remove it and extract the name) — aioobe
– aioobe, Commented Nov 14, 2010 at 15:39

aioobe · Accepted Answer · 2010-11-14 16:48:57Z

2

You could look for the ( and remove the remaining string.

public class Main {

    public static void main(String[] args) {

        String[] names = { "Jan vd Merwe", 
                           "Piet Breedt (172.166.23.41)",
                           "Jan vd Merwe (164.23.23.51)", 
                           "Sarel Fourie (23.12.167.244)" };

        for (String name : names) {

            int parIndex = name.indexLastOf('(');
            if (parIndex != -1)
                name = name.substring(0, parIndex-1);

            System.out.println(name);
        }
    }
}

prints:

Jan vd Merwe
Piet Breedt
Jan vd Merwe
Sarel Fourie

Another solution, based on regular expressions:

    String[] names = { "Jan vd Merwe", 
                       "Piet Breedt (172.166.23.41)",
                       "Jan vd Merwe (164.23.23.51)", 
                       "Sarel Fourie (23.12.167.244)" };

    String ipExp = "\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}\\.\\d{1,3}";
    Pattern pattern = Pattern.compile("(.*?)\\s*(\\(" + ipExp + "\\))?");

    for (String nameIp : names) {
        Matcher m = pattern.matcher(nameIp);
        if (m.matches()) {
            String name = m.group(1);
            String ip = m.group(2) == null ? "n/a" : m.group(2);
            System.out.printf("Name: %s, Ip: %s%n", name, ip);
        }
    }

Prints

Name: Jan vd Merwe, Ip: n/a
Name: Piet Breedt, Ip: (172.166.23.41)
Name: Jan vd Merwe, Ip: (164.23.23.51)
Name: Sarel Fourie, Ip: (23.12.167.244)

edited Nov 14, 2010 at 16:48

answered Nov 14, 2010 at 15:41

aioobe

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4 Comments

Jigar Joshi Over a year ago

your first solution will fail for Jan vd Merwe(Jan) such data

Tony Ennis Over a year ago

That's not in the 'spec'. It says IPs. Maybe the OP wants to keep the stuff in the parenthesis if it isn't an IP.

darioo Over a year ago

@org.life.java: That wasn't defined anywhere. No need to worry about special cases if OP is sure there aren't any.

aioobe Over a year ago

@org.life.java, changed to lastIndexOf... :-)

helpermethod · Accepted Answer · 2010-11-15 23:37:25Z

1

Use String.replace():

String myString = "Piet Breedt (172.166.23.41)";
// replace everything in between the parens (including the parens) by the empty String
myString = myString.replace("\(.*\)", "");

Of course, the regex could be specialised to only match ips, something like

\(\\d{1,3}\.\\d{1,3}\.\\d{1,3}.\\d{1,3}\)

EDIT

Here's how you would replace the lines in the files (pseudocode):

Open the original file. Open a temporary file.
Read line by line. This will give you a String for every line.
Remove the contents within the String. Write the new String to the temporary file.
When done, replace the original file by the temporary file.

edited Nov 15, 2010 at 23:37

answered Nov 14, 2010 at 15:50

helpermethod

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2 Comments

Vishwanath Over a year ago

regular expression should be \(\\d{1,3}\.\\d{1,3}\.\\d{1,3}.\\d{1,3}\)

Jaques Over a year ago

how would i use it without the array, ie what would i need to change.

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