如何在括号中查找元素[重复]

Question

我需要括号中的值作为文本字段中的注释。示例：

String text = "I have simple annotation @Test(value123) and ..

我可以找到带有值的注释本身，但我不明白如何在没有注释的情况下获取它 Pattern patternString = Pattern.compile("@Test\\(\\s+\\)");

结果：

@Test(value123)

但我需要

值123

Answer 1

添加(X)capturing group：

String text = "I have simple annotation @Test(value123) and ..";
Pattern p = Pattern.compile("@Test\\(([^)]*)\\)");
Matcher m = p.matcher(text);
if (m.find()) {
    System.out.println(m.group(1)); // Print capture group 1
}

输出

value123

解释

@Test\(     Match '@Test('
(           Start of capturing group 1
  [^)]*       Match zero-or-more characters, except ')'
)           End of capturing group 1
\)          Match ')'

---

或者，使用 (?<=X) zero-width positive lookbehind 和 (?=X) zero-width positive lookahead：

String text = "I have simple annotation @Test(value123) and ..";
Pattern p = Pattern.compile("(?<=@Test\\()[^)]*(?=\\))");
Matcher m = p.matcher(text);
if (m.find()) {
    System.out.println(m.group()); // Print matched text
}

输出

value123

解释

(?<=          Start of zero-width positive lookbehind
  @Test\(       Match '@Test('
)             End of zero-width positive lookbehind
[^)]*         Match zero-or-more characters, except ')'
(?=           Start of zero-width positive lookahead
  \)            Match ')'
)             End of zero-width positive lookahead

Answer 2

您可以使用匹配器，如下所示：

import java.util.regex.Pattern;
import java.util.regex.Matcher;

class Main {
  public static void main(String[] args) {
    String testString = "@Test(value123)";
    // unescaped parentheses catch the group
    // note that I changed \\s+ to .+,
    // since I want to match whatever is inside the parentheses,
    // not whitespaces (however, you should adjust it to your needs)
    Pattern pattern = Pattern.compile("@Test\\((.+)\\)");
    Matcher matcher = pattern.matcher(testString);
    if (matcher.matches()) {
      String value = matcher.group(1);
      System.out.println(value); // prints value123
    }
  }
}