4
\$\begingroup\$

What would be the best way to get the first two numbers of a string?

I can do it like this:

public static String getFirstTwoNumbersOfString(String s){
        if(s == null)
            return "";

        String numbers = "0123456789";

        String result = "";

        for(int i=0; i<s.length() && result.length()<2; i++){
            String c = String.valueOf(s.charAt(i));
            if(numbers.contains(c)){
                result += c;
            }
        }

        return result;
    }

But I think there must be a better way, more concise and with better performance.

\$\endgroup\$

1 Answer 1

Reset to default
2
\$\begingroup\$

In fact, you can:

public static String getFirstTwoNumbersOfString2(String s) {
    StringBuilder sb = new StringBuilder(2); // Capacity of 2 chars.

    for (char c : s.toCharArray()) {
        if (Character.isDigit(c)) {
            sb.append(c);

            if (sb.length() == 2) {
                break;
            }
        }
    }

    return sb.toString();
}

Above you can nicely ask Character whether a given character is a digit. Also, StringBuilder.append runs in constant amortized time unlike string concatenation which will build a copy of two concatenated strings.

Hope that helps.

\$\endgroup\$

You must log in to answer this question.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.