List Implementations That Use Arrays - Data Structures and Abstractions with Java - page 322

{ < Implementation deferred >
} // end replace

public T getEntry( int givenPosition)
{ < Implementation deferred >
} // end getEntry

public boolean contains(T anEntry)
{ < Implementation deferred >
} // end contains

public int getLength()
{

return numberOfEntries;
} // end getLength

public boolean isEmpty()
{

return numberOfEntries == 0; // or getLength() == 0
} // end isEmpty

public T[] toArray()
{

// the cast is safe because the new array contains null entries
@SuppressWarnings( "unchecked" )
T[] result = (T[]) new Object[numberOfEntries];

for ( int index = 0; index < numberOfEntries; index++)
{

result[index] = list[index];
} // end for

return result;
} // end toArray

// Doubles the size of the array list if it is full.
private void ensureCapacity()
{

if (numberOfEntries == list.length)
list = Arrays.copyOf(list, 2 * list.length);
} // end ensureCapacity

< This class will define two more private methods that will be discussed later. >
} // end AList

13.6

The core methods. As we just mentioned, we have chosen to implement the first add method and
the method toArray before the others, as they are central, or core, to our class. Adding a new
entry to the end of the list is easy; we simply add the entry to the array immediately after its last
occupied location. Of course, adding a new entry is possible only if the array has available space.
We call the private method ensureCapacity to resize the array if necessary. Thus, the first add