\A

描述 (Description)

边界匹配器[\A]匹配输入的开头。

例子 (Example)

以下示例显示了边界匹配器的用法。

package cn.xnip;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class BoundaryMatcherDemo {
   private static final String REGEX = "\\A";
   private static final String INPUT = "Welcome to xnip.cn";
   public static void main(String[] args) {
      // create a pattern
      Pattern  pattern = Pattern.compile(REGEX);
      // get a matcher object
      Matcher matcher = pattern.matcher(INPUT); 
      while(matcher.find()) {
         //Prints the start index of the match.
         System.out.println("Match String start(): "+matcher.start());
      }
   }
}

让我们编译并运行上面的程序，这将产生以下结果 -

Match String start(): 0