[Q#6341367][A#6341414] How to check if the string is a regular expression or not

https://stackoverflow.com/q/6341367

I have a string. How I can check if the string is a regular expression or contains regular expression or it is a normal string?

Answer

https://stackoverflow.com/a/6341414

The only reliable check you could do is if the String is a syntactically correct regular expression: Note, however, that this will result in true even for strings like Hello World and I'm not a regex, because technically they are valid regular expressions. The only cases where this will return false are strings that are not valid regular expressions, such as [unclosed character class or (unclosed group or +.

APIzation

boolean isRegex;
try {
  Pattern.compile(input);
  isRegex = true;
} catch (PatternSyntaxException e) {
  isRegex = false;
}

package com.stackoverflow.api;

import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

public class Human6341414 {

  public static boolean isStringRegex(String input) {
    //https://stackoverflow.com/a/6341414
    boolean isRegex;
    try {
      Pattern.compile(input);
      isRegex = true;
      return isRegex;
    } catch (PatternSyntaxException e) {
      isRegex = false;
      return isRegex;
    }
  }
}

package com.stackoverflow.api;

import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
 * How to check if the string is a regular expression or not
 *
 * @author APIzator
 * @see <a href="https://stackoverflow.com/a/6341414">https://stackoverflow.com/a/6341414</a>
 */
public class APIzator6341414 {

  public static void check(String input) throws Exception {
    boolean isRegex;
    try {
      Pattern.compile(input);
      isRegex = true;
    } catch (PatternSyntaxException e) {
      isRegex = false;
    }
  }
}