The collections api - Data Structures and Problem Solving Using Java - page 286

Consider the following implementation of the clear method (which
empties any collection).

6.15

public abstract class AbstractCollection<AnyType>
implements Collection<AnyType>
{
public void clear( )
{
Iterator<AnyType> itr = this.iterator( );

while( itr.hasNext( ) )
{
itr.next( );
itr.remove( );
}
}
...
}

Suppose LinkedList extends AbstractCollection and does not
override clear . What is the running time of clear ?

a.

Suppose ArrayList extends AbstractCollection and does not over-
ride clear . What is the running time of clear ?

b.

Suppose it takes 4 seconds to run clear on a 100,000-item ArrayList .
How long will it take to run clear on a 500,000-item ArrayList ?

c.

As clearly as possible, describe the behavior of this alternate
implementation of clear :

d.

public void clear( )
{
for( AnyType item : this )
this.remove( item );
}

Static method removeHalf removes the first half of a List (if there are
an odd number of items, then slightly less than one-half of the list is
removed). One possible implementation of removeHalf is shown
below:

6.16

public static void removeHalf( List<?> lst )
{
int size = lst.size( );

for( int i = 0; i < size / 2; i++ )
lst.remove( 0 );
}

a.

Why can't we use lst.size( )/2 as the test in the for loop?