Match IP addresses using regular expressions in Java


Since it was necessary to add a validation function for IP addresses and network settings using java, I implemented it using regular expressions. It is the memorandum.

How to use regular expressions in java

private boolean validateHoge(string target) {
    Pattern pattern = Pattern.compile("[Write a regular expression here]");
    final Matcher matcher = pattern.matcher(target);

    return matcher.matches();

You can now use regular expressions in java. matches () checks if the entire string matches, so use find () to check if part of the string matches the pattern.

IP address regular expression

// ~ 255.255.255.Up to 255
Pattern pattern = Pattern.compile("^(([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])[.]){3}([1-9]?[0-9]|1[0-9]{2}|2[0-4][0-9]|25[0-5])$");

It's straightforward, but I tried to express it like this.

Regular expressions I wrote incidentally

// 1 ~Up to 32
Pattern pattern = Pattern.compile("^([1-9]|[1-2][0-9]|3[0-1](.[0-9]+)?)|32$");

(I realized that it would be easier to change it to Integer after writing and limit it)

// 0~9, a~z, A~z, "."
Pattern pattern = Pattern.compile("[0-9a-zA-z.]+?");

A site where you can test regular expressions in java on your browser

This site was very convenient. It is useful when creating regular expressions because it shows the results for each method with matches () find ().

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