Java Reference
In-Depth Information
if
(topNode !=
null
)
top = topNode.getData();
return
top;
}
// end peek
6.5
Removing the top.
We pop, or remove, the top entry in the stack by setting
topNode
to the refer-
ence in the first node. Thus,
topNode
will reference what was the second node in the chain, as
Figure 6-3 shows. Moreover, the original first node will no longer be referenced, so it will be deal-
located. Since we also want the operation to return the stack's top entry before it is removed, the
method
pop
has the following implementation:
public
T pop()
{
T top = peek();
if
(topNode !=
null
)
topNode = topNode.getNextNode();
return
top;
}
// end pop
This operation also is O(1).
FIGURE 6-3
The stack (a) before and (b) after the first node in the chain is
deleted
Chain
(a)
topNode
Top entry of stack
Stack
(b)
topNode
Returned to client
top
Stack
