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Answer:

If str refers to an empty String object 

str.equals("")  is true, because both objects contain the same characters (they both contain no characters).

However, 

str == ""  is almost always false,

because the reference variable str almost always points to a different object than the particular object "". The == operator compares pointers, not what the pointers lead to. (Review Chapter 41 if this is unclear.)


The Rest of the String

So far the method looks like this: 

static int length( String str )
{
  if ( str.isEmpty() )           // or use str.equals("")
    return 0;
  
  else
    return 1 + length of all but first character of str;
}

But now there is another problem: How can you compute the length of all but the first character of the string?

This can be done by:

  1. Create a substring that omits the first character.
    • recall that the first character of a string is at position 0
  2. Use our length() on that substring


QUESTION 7:

(Review: ) What does this do: 

str.substring(1)

Assume str refers to a String object.


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