stack,是先进后出的一个堆栈，可是，因为他继承自vector，所以，vector很多功能他都具有。
stack和vector的关系应该是 has-a，而不是is-a
简单的操作有，push，top等
见例子如下：
import java.util.Stack;
public class StackExample {
public static void main (String args[]) {
Stack s = new Stack();
s.push("Autumnal Tints");
s.push("A Week on the Concord and Merrimack Rivers");
s.push("The Maine Woods");
// Check out what's next to read
System.out.println("Next: " + s.peek());
s.push("Civil Disobedience, Solitude and Life Without Principle");
// Read a book
System.out.println(s.pop());
s.push("Walden");
s.push("The Natural Man");
// Find that other book
int count = s.search("The Maine Woods");
while (count != −1 && count > 1) {
s.pop();
count−;
}
// Read a book
System.out.println(s.pop());
// Anything left?
System.out.println(s.empty());
}
}
看看源代码，不复杂：
public
class Stack<E> extends Vector<E> {
/**
* Creates an empty Stack.
*/
public Stack() {
}
/**
* Pushes an item onto the top of this stack. This has exactly
* the same effect as:
* <blockquote><pre>
* addElement(item)</pre></blockquote>
*
* @param item the item to be pushed onto this stack.
* @return the <code>item</code> 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 <tt>Vector</tt> 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 <tt>Vector</tt> 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 <code>true</code> if and only if this stack contains
* no items; <code>false</code> otherwise.
*/
public boolean empty() {
return size() == 0;
}
/**
* Returns the 1-based position where an object is on this stack.
* If the object <tt>o</tt> 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 <tt>1</tt>. The <tt>equals</tt>
* method is used to compare <tt>o</tt> 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 <code>-1</code>
* 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;
}