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Snowflake Common Package
There is a newer version: 5.1.4
package net.snowflake.common.util;

import java.util.regex.Pattern;

/**
 * This class wraps wildcard related functions and regular expression.
 *
 * @author hyu
 */
public class Wildcard
{
  /** Any single character */
  private static char SINGLE_CHAR = '_';

  /** O or more number of any characters */
  private static char MULTIPLE_CHAR = '%';

  /** escaped string */
  private static char ESCAPED_CHAR = '\\';

  private static String NON_ESCAPED_SINGLE_CHAR_REGEX = String.format("(? 0)
      {
        String strippedBlock = stripEscapedChar(block);
        regexBuilder.append(Pattern.quote(strippedBlock));
      }

      currentIndex += len;
      if (currentIndex < wildcardPattern.length())
      {
        char charToConvert = wildcardPattern.charAt(currentIndex);
        assert charToConvert == SINGLE_CHAR || charToConvert == MULTIPLE_CHAR;

        regexBuilder.append((charToConvert == SINGLE_CHAR) ? "." : ".*");
        currentIndex++;
      }
    }

    /* Deal with the special case that "abc" and "abc_" will both return only one
     * String by Pattern.split method (separator.split("abc_") will not return ["abc", ""])
     * But interestingly, separator.split("_abc") will return ["", "abc"]
     *
     * Also, separator.split("%%_") will return empty array.
     */
    while (currentIndex < wildcardPattern.length())
    {
      char charToConvert = wildcardPattern.charAt(currentIndex);
      assert charToConvert == SINGLE_CHAR || charToConvert == MULTIPLE_CHAR;
      regexBuilder.append((charToConvert == SINGLE_CHAR) ? "." : ".*");
      currentIndex ++;
    }
    return regexBuilder.toString();
  }

  /**
   * Converts a wild card pattern to regex
   * @param wildcardPattern a wild card pattern
   * @param isCaseSensitive is case insensitive?
   * @return a regex pattern
   */
  public static Pattern toRegexPattern(String wildcardPattern, boolean isCaseSensitive)
  {
    if (wildcardPattern == null)
      return null;

    return isCaseSensitive ?
        Pattern.compile(toRegexStr(wildcardPattern)) :
        Pattern.compile(toRegexStr(wildcardPattern), Pattern.CASE_INSENSITIVE);
  }

  /**
   * Used to determine if the input string is wildcard pattern
   * By wildcard pattern, we means a string contains '%' but not '\%'
   * or '_' but not '\_'
   * @param inputString a string
   * @return true if the string includes a wild card pattern
   */
  public static boolean isWildcardPatternStr(String inputString)
  {
    if (inputString == null)
      return false;
    return WILDCARD_STRING_PATTERN.matcher(inputString).matches();
  }

  /**
   * A helper function within toRegexStr(String) method.
   * For each substring, remove the escaped char '\'
   * @param inputString a string
   * @return a string without escaped chars
   */
  private static String stripEscapedChar(String inputString)
  {
    StringBuilder sb = new StringBuilder();
    boolean escaped = false;
    for (int i=0; i