Creating pattern for searching an exact number in java

Question

i have a .txt file, which looks like this(just example):

sfafsaf102030

asdasa203040

asdaffa304050

sadasd405060

I am trying to get whole line which contains a specific(given by me) number, for example i have number "203040" and i want to receive "asdasa203040".

I tried something like this:

File file = new File("file.txt");
Scanner sc = new Scanner(file);

String pattern = "(.*)(\\d+)";
Pattern p = Pattern.compile(pattern);

System.out.println(sc.findInLine(pattern));

but it only gives me line with any number and not the one i specified. How to change it?

Thanks.

Answer 1

You don't need to use regex for this. You could just check for the line containing the number you enter:

File file = new File("file.txt");
Scanner sc = new Scanner(file);
Scanner input = new Scanner(System.in);

System.out.println(/*prompt user for input here*/);

String number = input.next();
String line;
while (sc.hasNextLine()) {
    line = sc.nextLine();
    if (line.contains(number)) {
        System.out.println(line);
        break;
    } else if (!sc.hasNextLine()) {
        System.out.println("Line not found.");
    }
}