Java中的正则表达式\ Q元字符
子表达式/元字符“\Q”会转义所有字符，直到“\E”为止；即，您可以通过将正则表达式中的元字符放在\Q和\E之间来转义。例如，表达式[aeiou]匹配其中带有元音字母的字符串。
例
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class SampleProgram {
public static void main( String args[] ) {
String regex = "[aeiou]";
Scanner sc = new Scanner(System.in);
System.out.println("Enter input string: ");
String input = sc.nextLine();
//创建一个Pattern对象
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);
if(matcher.find()) {
System.out.println("Match occurred");
} else {
System.out.println("Match not occurred");
}
}
}输出结果
Enter input string: sample Match occurred
但是，如果您在\Q和\E中使用与\Q[aeiou]\E相同的表达式，则它将与给定字符串中的字符“[aeiou]”相同序列。简而言之，元字符失去了意义，将被视为普通字符
示例
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class SampleProgram {
public static void main( String args[] ) {
String regex = "\\Q[aeiou]\\E";
Scanner sc = new Scanner(System.in);
System.out.println("Enter input string: ");
String input = sc.nextLine();
//创建一个Pattern对象
Pattern pattern = Pattern.compile(regex);
Matcher matcher = pattern.matcher(input);
if(matcher.find()) {
System.out.println("Match occurred");
} else {
System.out.println("Match not occurred");
}
}
}输出1
Enter input string: sample Match not occurred
输出2
Enter input string: The letters [aeiou] are vowels in English alphabet Match occurred