Stack class represents a last-in-first-out
- * (LIFO) stack of objects. It extends class Vector with five
- * operations that allow a vector to be treated as a stack. The usual
- * push and pop operations are provided, as well as a
- * method to peek at the top item on the stack, a method to test
- * for whether the stack is empty, and a method to search
- * the stack for an item and discover how far it is from the top.
- * - * When a stack is first created, it contains no items. - * - *
A more complete and consistent set of LIFO stack operations is - * provided by the {@link Deque} interface and its implementations, which - * should be used in preference to this class. For example: - *
{@code
- * Deque stack = new ArrayDeque();}
- *
- * @author Jonathan Payne
- * @since JDK1.0
- */
-public
-class Stack- * - * @param item the item to be pushed onto this stack. - * @return the- * addElement(item)
item argument.
- * @see java.util.Vector#addElement
- */
- public E push(E item) {
- addElement(item);
-
- return item;
- }
-
- /**
- * Removes the object at the top of this stack and returns that
- * object as the value of this function.
- *
- * @return The object at the top of this stack (the last item
- * of the Vector object).
- * @throws EmptyStackException if this stack is empty.
- */
- public synchronized E pop() {
- E obj;
- int len = size();
-
- obj = peek();
- removeElementAt(len - 1);
-
- return obj;
- }
-
- /**
- * Looks at the object at the top of this stack without removing it
- * from the stack.
- *
- * @return the object at the top of this stack (the last item
- * of the Vector object).
- * @throws EmptyStackException if this stack is empty.
- */
- public synchronized E peek() {
- int len = size();
-
- if (len == 0)
- throw new EmptyStackException();
- return elementAt(len - 1);
- }
-
- /**
- * Tests if this stack is empty.
- *
- * @return true if and only if this stack contains
- * no items; false otherwise.
- */
- public boolean empty() {
- return size() == 0;
- }
-
- /**
- * Returns the 1-based position where an object is on this stack.
- * If the object o occurs as an item in this stack, this
- * method returns the distance from the top of the stack of the
- * occurrence nearest the top of the stack; the topmost item on the
- * stack is considered to be at distance 1. The equals
- * method is used to compare o to the
- * items in this stack.
- *
- * @param o the desired object.
- * @return the 1-based position from the top of the stack where
- * the object is located; the return value -1
- * indicates that the object is not on the stack.
- */
- public synchronized int search(Object o) {
- int i = lastIndexOf(o);
-
- if (i >= 0) {
- return size() - i;
- }
- return -1;
- }
-
- /** use serialVersionUID from JDK 1.0.2 for interoperability */
- private static final long serialVersionUID = 1224463164541339165L;
-}