guava/src/com/google/common/base/Ascii.java
public static String toLowerCase(CharSequence chars) {
    if (chars instanceof String) {
      return toLowerCase((String) chars);
    }
    char[] newChars = new char[chars.length()];
    for (int i = 0; i < newChars.length; i++) {
      newChars[i] = toLowerCase(chars.charAt(i));
    }
    return String.valueOf(newChars);
  }
public static String toLowerCase(CharSequence chars) {
    if (chars instanceof String) {
      return toLowerCase((String) chars);
    }
    char[] newChars = new char[chars.length()];
    for (int i = 0; i < newChars.length; i++) {
      newChars[i] = toLowerCase(chars.charAt(i));
    }
    return String.valueOf(newChars);
  }
public static String toLowerCase ( CharSequence chars ) { if ( chars instanceof String ) { return toLowerCase ( ( String ) chars ) ; } char [ ] newChars = new char [ chars . length ( ) ] ; for ( int i = 0 ; i < newChars . length ; i ++ ) { newChars [ i ] = toLowerCase ( chars . charAt ( i ) ) ; } return String . valueOf ( newChars ) ; }
Returns a copy of the input character sequence in which all {@linkplain #isUpperCase(char)
uppercase ASCII characters} have been converted to lowercase. All other characters are copied
without modification.

@since 14.0
Returns a copy of the input character sequence in which all { @linkplain #isUpperCase ( char ) uppercase ASCII characters } have been converted to lowercase . All other characters are copied without modification .