Computer Science 1 Top Lectures Assignments Noticeboard Arrays vs Vectors

Reading: 10.9

• Advantages of arrays:
1. Store primitives
2. More efficient: can access w/o sending a message
3. Restricted - can only be of one type!
• Disadvantages of arrays:
1. Fixed (or static)
2. Limited operations, e.g., no insertElementAt
3. Restricted - can only be of one type!
• Summary:

	Array a	Vector v
Element type	declaration of a, e.g., int a[10], so each element is an int	reference to Object (must cast)
Element referenced by	a[index]	(cast)v.elementAt(index) TYPOS IN BOOK
Element assignment by	a[index] = ...	v.setElementAt (Object obj, index) TYPO IN BOOK
Number of elements	a.length	v.size()
Things it can store	primitive and classes (objects)	classes (objects)
Dynamic	NO	YES
Defined by	Java language	Java class library

• Many patterns that we used for Vectors also work for arrays:

boolean search(String s) { // Returns true if and only if s equals one
                           // of the Strings in v.
  int k;       // k== the index of the next position in 
               //      the array to check.
               // No match has been found in positions 
               //      0 through k-1.
  k = 0;
  while (k!=v.length && !s.equals(v[k]))
     k++;
  // k==v.length || s.equals(v[k])
     return k!=v.length;
}

• However some things don't map quite as nicely, e.g., insertElementAt