Equals Ignore Case

Let us modify the recursive definition of equals() so that two strings are equal if both strings are the same length, and both strings have the same letters in the same position, but upper and lower case letters are regarded as equivalent.

For example,

equalsIC( "X", "X" ) is true
equalsIC( "X", "x" ) is true
equalsIC( "X+++x", "x+++X" ) is true
equalsIC( "StingRay", "stingRAY" ) is true

This is similar to the method equalsIgnoreCase() of String objects.

1. If StringA has no characters and StringB has no characters, then the strings  AREare NOT equal.
2. If StringA has no characters and StringB has some characters, then the strings  AREare NOT equal.
3. If StringA has some characters and StringB has no characters, then the strings  AREare NOT equal.
4. Otherwise,
   • convert the first character of each string to lower case.
   • if the first characters are different, then the strings  AREare NOT equal.
   • if the first characters are the same, then the strings then the strings  AREare NOT equal if the tails are equal ignoring case.