我如何使用正则表达式Java提取值？

Question

我需要单独从此文本中提取数字，我使用子字符串提取一些细节，有时数字减少，所以我得到一个错误值...

 example(16656);

Answer 1

Use Pattern to compile your regular expression and Matcher to get a particular captured group. The regex I'm using is:

example\((\d+)\)

which captures the digits ( \\d+ ) within the parentheses. So:

Pattern p = Pattern.compile("example\\((\\d+)\\)");
Matcher m = p.matcher(text);
if (m.find()) {
  int i = Integer.valueOf(m.group(1));
  ...
}

Answer 2

look at Java Regular Expression sample here:

http://java.sun.com/developer/technicalArticles/releases/1.4regex/

specially focus on find method.

Answer 3

String yourString = "example(16656);";

Pattern pattern = Pattern.compile("\\w+\\((\\d+)\\);");
Matcher matcher = pattern.matcher(yourString);
if (matcher.matches())
{
    int value = Integer.parseInt(matcher.group(1));
    System.out.println("Your number: " + value);
}

Answer 4

I will suggest you to write your own logic to do this. Using Pattern and Matcher things from java are good practice but these are standard solutions and may not suit as a solution in effective manner always. Like cletus provided a very neat solution but what happens in this logic is that a substring matching algorithm is performed in the background to trace digits. You do not need the pattern finding here I suppose. You just need to extract the digits from a string (like 123 from "a1b2c3") .See the following code which does it in clean manner in O(n) and does not perform unnecessary extra operation as Pattern and Matcher classes do for you (just do copy and paste and run :) ):

public class DigitExtractor {

/**
 * @param args
 */
public static void main(String[] args) {

    String sample = "sdhj12jhj345jhh6mk7mkl8mlkmlk9knkn0";

    String digits = getDigits(sample);

    System.out.println(digits);
}

private static String getDigits(String sample) {

    StringBuilder out = new StringBuilder(10);

    int stringLength = sample.length();

    for(int i = 0; i <stringLength ; i++)
    {
        char currentChar = sample.charAt(i);
        int charDiff = currentChar -'0';

        boolean isDigit = ((9-charDiff)>=0&& (9-charDiff <=9));

        if(isDigit)
            out.append(currentChar);

    }

    return out.toString();
}

}