Java正则表达式逻辑运算符

Java Regular expressions supports 3 logical operators they are −

• XY: X followed by Y

• X|Y: X or Y

• (X): capturing group.

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XY: X followed by Y

This simply matches two single consecutive characters.

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Example

 Live Demo

import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class Test {
   public static void main(String[] args) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter input text: ");
      String input = sc.nextLine();
      String regex = "am";
      //Creating a pattern object
      Pattern pattern = Pattern.compile(regex);
      //Matching the compiled pattern in the String
      Matcher matcher = pattern.matcher(input);
      if (matcher.find()) {
         System.out.println("Match occurred");
      } else {
         System.out.println("Match not occurred");
      }
   }
}

Output 1

输出 1

Enter input text:
sample text
Match occurred

Output 2

Enter input text:
hello how are you
Match not occurred

X|Y

This matches either of the two expressions/characters surrounding "|"

Example

 Live Demo

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexExample {
   public static void main( String args[] ) {
      String regex = "Hello|welcome";
      String input = "Hello how are you welcome to Tutorialspoint";
      Pattern pattern = Pattern.compile(regex);
      Matcher matcher = pattern.matcher(input);
      int count = 0;
      while(matcher.find()) {
         count++;
      }
      System.out.println("Number of matches: "+count);
   }
}

输出

Number of matches: 2

(X): 捕获组

捕获组允许您将多个字符视为一个单元。您只需将这些字符放在一对括号中即可。

示例

 实时演示

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

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