Common Java Regex Examples

Here we use weak/strong to denote more/less permissive respectively


public static final String specialChar = "^([-!@#$%^&*(){}:;,<>\\.?\\]\\\\\\\"\\_\\+\\|\\'\\/\\=\~\\`\\[]|[\\\\s]|)+$";
public static final String weakHTML = "<.*>.*";
public static final String strongHTML = "\\s]+))?)+\\s*|\\s*)/?>";
public static final String weakEmail = ".+@.+\\..+";
public static final String strongEmail = "(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|\"(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21\\x23-\\x5b\\x5d-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])*\")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\\x01-\\x08\\x0b\\x0c\\x0e-\\x1f\\x21-\\x5a\\x53-\\x7f]|\\\\[\\x01-\\x09\\x0b\\x0c\\x0e-\\x7f])+)\\])";
public static final String alphaNumeric = "^([A-Z]|[a-z]|[0-9]|[\\s]|)*$";
public static final String normalSentence = "^([A-Z]|[a-z]|[0-9]|[\\s]|[\\.!\",])*$";


Now use those in the context of a helper function


    public static final String alphaNumeric = "^([A-Z]|[a-z]|[0-9]|[\\s]|)*$";

    public static boolean isAlphaNumeric(String string) {
        //Null check and blank check!
        //Null check first! Ki-yah!
        if (string != null && !string.isEmpty()) {
            return string.matches(alphaNumeric);
        } else {
            return false;
        }
    }