You can also use NumberUtil.isNumber(String str) from Apache Commons

Just try with following regex:

private static final String DIGIT_PATTERN = "\\d+";

Check this it might help you

String regex = "\\d+";
System.out.println("abc45hdg".matches(regex));

If you want to extract the first number out of the input string, you can do-

public static String extractNumber(final String str) {                
    
    if(str == null || str.isEmpty()) return "";
    
    StringBuilder sb = new StringBuilder();
    boolean found = false;
    for(char c : str.toCharArray()){
        if(Character.isDigit(c)){
            sb.append(c);
            found = true;
        } else if(found){
            // If we already found a digit before and this char is not a digit, stop looping
            break;                
        }
    }
    
    return sb.toString();
}

Examples:

For input "123abc", the method above will return 123.

For "abc1000def", 1000.

For "555abc45", 555.

For "abc", will return an empty string.

Here's my attempt. Note, this uses unicode categories for validation so is non-latin language friendly.

import java.util.regex.Pattern;

public class PasswordValidator {

    public static void main(String[] args) {
        final PasswordValidator passwordValidator = new PasswordValidator();
        for (String password : new String[] { "abc", "abc123", "ABC123", "abc123ABC", "!!!AAabas1", "гшщз",
                "гшщзЧСМИ22" }) {
            System.out.printf("Password '%s' is %s%n", password, passwordValidator.isValidPassword(password) ? "ok"
                    : "INVALID");
        }
    }
    private static final Pattern LOWER_CASE = Pattern.compile("\\p{Lu}");
    private static final Pattern UPPER_CASE = Pattern.compile("\\p{Ll}");
    private static final Pattern DECIMAL_DIGIT = Pattern.compile("\\p{Nd}");

    /**
     * Determine if a password is valid.
     * 
     * <p>
     * A password is considered valid if it contains:
     * <ul>
     * <li>At least one lower-case letter</li>
     * <li>At least one upper-case letter</li>
     * <li>At least one digit</li>
     * </p>
     * 
     * @param password
     *            password to validate
     * @return True if the password is considered valid, otherwise false
     */
    public boolean isValidPassword(final String password) {
        return containsDigit(password) && containsLowerCase(password) && containsUpperCase(password);
    }

    private boolean containsDigit(final String str) {
        return DECIMAL_DIGIT.matcher(str).find();
    }

    private boolean containsUpperCase(final String str) {
        return UPPER_CASE.matcher(str).find();
    }

    private boolean containsLowerCase(final String str) {
        return LOWER_CASE.matcher(str).find();
    }

}

Here's the output:

Password 'abc' is INVALID
Password 'abc123' is INVALID
Password 'ABC123' is INVALID
Password 'abc123ABC' is ok
Password '!!!AAabas1' is ok
Password 'гшщз' is INVALID
Password 'гшщзЧСМИ22' is ok

Replace any instance of one or more digits with the system line separator followed by the matched digit(s).

As such:

String  s = "S.No.DistrictMarketPrice 1 Agra Achhnera NIL 2 Agra Agra NIL 3 Agra Fatehabad NIL 4 Agra Fatehpur Sikri NIL 5 Agra Jagner NIL 6 Agra Jarar NIL 7 Agra Khairagarh NIL 8 Agra Shamshabad NIL 9 Aligarh Atrauli NIL 10 Aligarh Chharra NIL";

System.out.println(
    s.replaceAll("\\d+", System.getProperty("line.separator") + "$0")
);

Output

S.No.DistrictMarketPrice 
1 Agra Achhnera NIL 
2 Agra Agra NIL 
3 Agra Fatehabad NIL 
4 Agra Fatehpur Sikri NIL 
5 Agra Jagner NIL 
6 Agra Jarar NIL 
7 Agra Khairagarh NIL 
8 Agra Shamshabad NIL 
9 Aligarh Atrauli NIL 
10 Aligarh Chharra NIL

You should extract the validation, meaning the checking if the string only contains digits, to a separate method like so

private static boolean containsOnlyDigits(final String value) {
    for (int i = 0; i < value.length(); i++) {
        if(!Character.isDigit(value.charAt(i))) {
            return false;
        }
    }
    return true;
}  

and use it in the setMobile() method like so

public void setMobile(String mobile) {
    if(containsOnlyDigits(mobile)) {
        this.mobile = mobile;
    }
}  

So each method is doing only one thing.

Because the method setMobile() is public you should check if the passed mobile is not null.

Disclaimer: Written in the editor without testing.

If you really want to find single digits, you need this:

Pattern pattern = Pattern.compile("\\d");
Matcher matcher = pattern.matcher(testline);
while (matcher.find()) {
    System.out.println(matcher.group());
}

if you want to find non-floating-point numbers, change the regex to "\\d+".