Bag Implementations That Use Arrays - Data Structures and Abstractions with Java - page 30

If we are adding to an empty bag, numberOfEntries would be zero, and the assignment would be to
bag[0] . If the bag contained one entry, an additional entry would be assigned to bag[1] , and so on.
After each addition to the bag, we increase the counter numberOfEntries . These steps are illus-
trated in Figure 2-3 and accomplished by the definition of the method add that follows the figure.

FIGURE 2-3

Adding entries to an array that represents a bag, whose capacity
is six, until it becomes full

bag numberOfEntries

Empty

0

0 1 2 3 4 5

Doug

1

0 1 2 3 4 5

Doug Nancy

Nancy

2

1 2 3 4 5

0

Doug Nancy Ted

Nancy

3

0 1 2 3 4 5

Doug Nancy Ted Vandee

Nancy

4

1 2 3 4 5

0

Doug

Nancy Ted Vandee Sue

5

0 1 2 3 4 5

Full Doug Nancy Sue Frank

Ted Vandee 6

0 1 2 3 4 5

/** Adds a new entry to this bag.
@param newEntry the object to be added as a new entry
@return true if the addition is successful, or false if not */
public boolean add(T newEntry)
{

boolean result = true ;
if (isFull())
{

result = false ;

}
else
{ // assertion: result is true here
bag[numberOfEntries] = newEntry;
numberOfEntries++;
} // end if
return result;
} // end add