非捕获组Java正则表达式：
使用捕获组，您可以将多个字符视为一个单元。您只需要将要分组的字符放在一组括号内即可。例如-
(.*)(\\d+)(.*)
如果您要匹配多个组，则将捕获每个组的匹配结果。您可以通过将其各自的组号传递给group()方法来获得一个组的结果。1,2，3等。（从右到左）组0表示整个匹配。
示例
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CapturingGroups {
public static void main( String args[] ) {
System.out.println("Enter input text");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
String regex = "(.*)(\\d+)(.*)";
//Create a Pattern object
Pattern pattern = Pattern.compile(regex);
//Now create matcher object.
Matcher matcher = pattern.matcher(input);
if (matcher.find( )) {
System.out.println("Found value: " + matcher.group(0) );
System.out.println("Found value: " + matcher.group(1) );
System.out.println("Found value: " + matcher.group(2) );
System.out.println("Found value: " + matcher.group(3) );
} else {
System.out.println("NO MATCH");
}
}
}输出结果
Enter input text sample data with 1234 (digits) in middle Found value: sample data with 1234 (digits) in middle Found value: sample data with 123 Found value: 4 Found value: (digits) in middle
非捕获组
非捕获组提供与捕获组相同的功能，但不捕获结果
例如，如果您需要使用组来匹配文本中的URL或电话号码，由于所需子字符串的开头部分相同，因此您无需捕获某些组的结果，在这种情况下，您可以使用非捕获组。非捕获组以（？：开头，以）结尾。
示例
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class CapturingGroups {
public static void main( String args[] ) {
System.out.println("Enter input text");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
String regex = "(.*)(?:\\d+)(.*)";
//Create a Pattern object
Pattern pattern = Pattern.compile(regex);
//Now create matcher object.
Matcher matcher = pattern.matcher(input);
if (matcher.find( )) {
System.out.println("Found value: " + matcher.group(0) );
System.out.println("Found value: " + matcher.group(1) );
System.out.println("Found value: " + matcher.group(2) );
} else {
System.out.println("NO MATCH");
}
}
}输出结果
Enter input text sample data with 1234 (digits) in middle Found value: sample data with 1234 (digits) in middle Found value: sample data with 123 Found value: (digits) in middle
注意：非捕获组将不包括在组计数中。