Collections and Generics - SCJP Sun Certified Programmer for Java Platform SE6 - page 440

The methods demonstrated here are in the List interface and therefore are available to
all List objects. Each implementation class of List also adds additional behaviors relevant
to the type of list. For example:
The LinkedList class implements a doubly linked list and contains the methods
addFirst , addLast , removeFirst , and removeLast for adding and removing elements at
the beginning or end of the linked list.
The Stack class contains the methods push and pop for pushing and popping elements
onto the stack, as demonstrated in the sidebar “The Stack Class.”
The Vector class contains methods for array-like behaviors, like elementAt ,
insertElementAt , and removeElementAt .
The ArrayList class is a simple (but useful) implementation of the List interface and
basically contains the same methods as the List interface.
The Stack Class
The Stack class in java.util implements a Stack data structure as a list. The Stack class
defi nes a push method that pushes an item on the stack and a pop method that removes the
top object from the stack. For example, the following statements create a Stack for storing
Integer objects and push two elements onto the stack:
Stack<Integer> mystack = new Stack<Integer>();
mystack.push(new Integer(100));
mystack.push(200);
Due to generics, only Integer types can be pushed on the Stack mystack . (Pushing 200
is allowed because of Java's autoboxing feature.) The following line of code does not
compile:
mystack.push(“Not an Integer”);
The compiler error looks like
ListDemo.java:9: push(java.lang.Integer) in
java.util.Stack<java.lang.Integer> cannot be applied to
(java.lang.String)
mystack.push(“Not an Integer”);
^
The pop method of stack removes the top element and returns a reference to it. For
example:
Integer top = mystack.pop();
for(Integer i : mystack) {
System.out.println(i);
}