content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.csp.sentinel.util;
  
  /***
   * Util class providing operations on {@link String}.
   *
   * @author youji.zj
   */
  public final class StringUtil {
  
      public static final String EMPTY = "";
  
      public static boolean equalsIgnoreCase(final CharSequence str1, final CharSequence str2) {
          if (str1 == null || str2 == null) {
              return str1 == str2;
          } else if (str1 == str2) {
              return true;
          } else if (str1.length() != str2.length()) {
              return false;
          } else {
              return regionMatches(str1, true, 0, str2, 0, str1.length());
          }
      }
  
      public static boolean equals(String str1, String str2) {
          return str1 == null ? str2 == null : str1.equals(str2);
      }
  
      public static boolean isBlank(String str) {
          int strLen;
          if (str == null || (strLen = str.length()) == 0) {
              return true;
          }
          for (int i = 0; i < strLen; i++) {
              if ((!Character.isWhitespace(str.charAt(i)))) {
                  return false;
              }
          }
          return true;
      }
  
      public static boolean isNotBlank(String str) {
          return !isBlank(str);
      }
  
      public static boolean isEmpty(String str) {
          return str == null || str.length() == 0;
      }
  
      public static boolean isNotEmpty(String str) {
          return !isEmpty(str);
      }
  
      public static String trimToEmpty(String str) {
          return str == null ? EMPTY : str.trim();
      }
  
      public static String trim(String str) {
          return str == null ? null : str.trim();
      }
  
      private static boolean regionMatches(final CharSequence cs, final boolean ignoreCase, final int thisStart,
                                           final CharSequence substring, final int start, final int length) {
          if (cs instanceof String && substring instanceof String) {
              return ((String)cs).regionMatches(ignoreCase, thisStart, (String)substring, start, length);
          }
          int index1 = thisStart;
          int index2 = start;
          int tmpLen = length;
  
          // Extract these first so we detect NPEs the same as the java.lang.String version
          final int srcLen = cs.length() - thisStart;
          final int otherLen = substring.length() - start;
  
          // Check for invalid parameters
          if (thisStart < 0 || start < 0 || length < 0) {
              return false;
          }
  
          // Check that the regions are long enough
          if (srcLen < length || otherLen < length) {
              return false;
          }
  
          while (tmpLen-- > 0) {
              final char c1 = cs.charAt(index1++);
              final char c2 = substring.charAt(index2++);
  
              if (c1 == c2) {
                  continue;
              }
  
              if (!ignoreCase) {
                  return false;
              }
  
              // The same check as in String.regionMatches():
              if (Character.toUpperCase(c1) != Character.toUpperCase(c2)
                  && Character.toLowerCase(c1) != Character.toLowerCase(c2)) {
                  return false;
              }
          }
  
          return true;
      }
  
      public static String capitalize(String str) {
          return changeFirstCharacterCase(str, true);
      }
  
      private static String changeFirstCharacterCase(String str, boolean capitalize) {
          if (str == null || str.length() == 0) {
              return str;
          }
          StringBuilder buf = new StringBuilder(str.length());
          if (capitalize) {
              buf.append(Character.toUpperCase(str.charAt(0)));
          } else {
              buf.append(Character.toLowerCase(str.charAt(0)));
          }
          buf.append(str.substring(1));
          return buf.toString();
      }
  }
  