98 lines
2.7 KiB
Java
98 lines
2.7 KiB
Java
|
|
||
|
|
package java.util;
|
||
|
|
|
||
|
|
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;
|
||
|
|
}
|