Regex matching with pattern and matches

Question

I am reading input from file it contains set of lines as below :

BDI100                 172.20.1.5      YES TFTP   up                    up
    BDI500                 172.20.1.50     YES TFTP   up                    up
    BDI600                 172.20.1.58     YES TFTP   up                    up

I have to extract the complete line which contains only 172.20.1.5

Below is my code :

while ((line = lineNumberReader.readLine()) != null) {
        Pattern p = Pattern.compile(expr.trim()); /*expr is filter contains 172.20.1.5 */
        Matcher m = p.matcher(line);
        if(m.find()){
            System.out.println(line);
        }
    }

I am expexting output as :

BDI100                 172.20.1.5      YES TFTP   up                    up

But is printing all the lines.

Answer 1

This will help you:

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {

    public static void main(String[] args) {
        String[] lines = new String[]{"BDI100                 172.20.1.5      YES TFTP   up                    up",
            "BDI500                 172.20.1.50     YES TFTP   up                    up",
            "BDI600                 172.20.1.58     YES TFTP   up                    up"};
        Pattern p = Pattern.compile("172\\.20\\.1\\.5\\s");
        for (String line : lines) {
            Matcher m = p.matcher(line);
            if (m.find()) {
                System.out.println(line);
            }
        }
    }

}

Answer 2

What you are doing seems a little excessive. Perhaps try this:

String need = "172.20.1.5";
String line = "";
while ((line = lineNumberReader.readLine()) != null) {
    if (line.trim().equals("")) {
        continue:
    }
    if (line.contains(need) {
        System.out.println(line);
        break;
    }
}

Answer 3

/*Intialize expr within braces */
String expr = "(172.20.1.5 )";
while ((line = lineNumberReader.readLine()) != null) {
        Pattern p = Pattern.compile(expr.trim()); /*expr is filter contains 172.20.1.5 */
        Matcher m = p.matcher(line);
        if(m.find()){
            System.out.println(line);
        }
    }