Class Stack<E>

java.lang.Object

java.util.AbstractCollection<E>

java.util.AbstractList<E>

java.util.Vector<E>

java.util.Stack<E>

Type Parameters:

E - Type of component elements

All Implemented Interfaces:

Serializable, Cloneable, Iterable<E>, Collection<E>, List<E>, RandomAccess, SequencedCollection<E>

public class Stack<E>
extends Vector<E>

The 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 Deque interface and its implementations, which should be used in preference to this class. For example:

  Deque<Integer> stack = new ArrayDeque<Integer>();

Since:

1.0

See Also:

• Serialized Form

Field Summary

Fields declared in class Vector

capacityIncrement, elementCount, elementData

Modifier and Type	Field	Description
protected int	capacityIncrement	The amount by which the capacity of the vector is automatically incremented when its size becomes greater than its capacity.
protected int	elementCount	The number of valid components in this Vector object.
protected Object[]	elementData	The array buffer into which the components of the vector are stored.

Fields declared in class AbstractList

modCount

Modifier and Type	Field	Description
protected int	modCount	The number of times this list has been structurally modified.

Constructor Summary

Constructors

Constructor	Description
Stack()	Creates an empty Stack.

Method Summary

Modifier and Type	Method	Description
boolean	empty()	Tests if this stack is empty.
E	peek()	Looks at the object at the top of this stack without removing it from the stack.
E	pop()	Removes the object at the top of this stack and returns that object as the value of this function.
E	push(E item)	Pushes an item onto the top of this stack.
int	search(Object o)	Returns the 1-based position where an object is on this stack.

Methods declared in class Vector

add, add, addAll, addAll, addElement, capacity, clear, clone, contains, containsAll, copyInto, elementAt, elements, ensureCapacity, equals, firstElement, forEach, get, hashCode, indexOf, indexOf, insertElementAt, isEmpty, iterator, lastElement, lastIndexOf, lastIndexOf, listIterator, listIterator, remove, remove, removeAll, removeAllElements, removeElement, removeElementAt, removeIf, removeRange, replaceAll, retainAll, set, setElementAt, setSize, size, spliterator, subList, toArray, toArray, toString, trimToSize

Modifier and Type	Method	Description
void	add(int index, E element)	Inserts the specified element at the specified position in this Vector.
boolean	add(E e)	Appends the specified element to the end of this Vector.
boolean	addAll(int index, Collection<? extends E> c)	Inserts all of the elements in the specified Collection into this Vector at the specified position.
boolean	addAll(Collection<? extends E> c)	Appends all of the elements in the specified Collection to the end of this Vector, in the order that they are returned by the specified Collection's Iterator.
void	addElement(E obj)	Adds the specified component to the end of this vector, increasing its size by one.
int	capacity()	Returns the current capacity of this vector.
void	clear()	Removes all of the elements from this Vector.
Object	clone()	Returns a clone of this vector.
boolean	contains(Object o)	Returns true if this vector contains the specified element.
boolean	containsAll(Collection<?> c)	Returns true if this Vector contains all of the elements in the specified Collection.
void	copyInto(Object[] anArray)	Copies the components of this vector into the specified array.
E	elementAt(int index)	Returns the component at the specified index.
Enumeration<E>	elements()	Returns an enumeration of the components of this vector.
void	ensureCapacity(int minCapacity)	Increases the capacity of this vector, if necessary, to ensure that it can hold at least the number of components specified by the minimum capacity argument.
boolean	equals(Object o)	Compares the specified Object with this Vector for equality.
E	firstElement()	Returns the first component (the item at index 0) of this vector.
void	forEach(Consumer<? super E> action)	Performs the given action for each element of the Iterable until all elements have been processed or the action throws an exception.
E	get(int index)	Returns the element at the specified position in this Vector.
int	hashCode()	Returns the hash code value for this Vector.
int	indexOf(Object o)	Returns the index of the first occurrence of the specified element in this vector, or -1 if this vector does not contain the element.
int	indexOf(Object o, int index)	Returns the index of the first occurrence of the specified element in this vector, searching forwards from index, or returns -1 if the element is not found.
void	insertElementAt(E obj, int index)	Inserts the specified object as a component in this vector at the specified index.
boolean	isEmpty()	Tests if this vector has no components.
Iterator<E>	iterator()	Returns an iterator over the elements in this list in proper sequence.
E	lastElement()	Returns the last component of the vector.
int	lastIndexOf(Object o)	Returns the index of the last occurrence of the specified element in this vector, or -1 if this vector does not contain the element.
int	lastIndexOf(Object o, int index)	Returns the index of the last occurrence of the specified element in this vector, searching backwards from index, or returns -1 if the element is not found.
ListIterator<E>	listIterator()	Returns a list iterator over the elements in this list (in proper sequence).
ListIterator<E>	listIterator(int index)	Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
E	remove(int index)	Removes the element at the specified position in this Vector.
boolean	remove(Object o)	Removes the first occurrence of the specified element in this Vector If the Vector does not contain the element, it is unchanged.
boolean	removeAll(Collection<?> c)	Removes from this Vector all of its elements that are contained in the specified Collection.
void	removeAllElements()	Removes all components from this vector and sets its size to zero.
boolean	removeElement(Object obj)	Removes the first (lowest-indexed) occurrence of the argument from this vector.
void	removeElementAt(int index)	Deletes the component at the specified index.
boolean	removeIf(Predicate<? super E> filter)	Removes all of the elements of this collection that satisfy the given predicate (optional operation).
protected void	removeRange(int fromIndex, int toIndex)	Removes from this list all of the elements whose index is between fromIndex, inclusive, and toIndex, exclusive.
void	replaceAll(UnaryOperator<E> operator)	Replaces each element of this list with the result of applying the operator to that element (optional operation).
boolean	retainAll(Collection<?> c)	Retains only the elements in this Vector that are contained in the specified Collection.
E	set(int index, E element)	Replaces the element at the specified position in this Vector with the specified element.
void	setElementAt(E obj, int index)	Sets the component at the specified index of this vector to be the specified object.
void	setSize(int newSize)	Sets the size of this vector.
int	size()	Returns the number of components in this vector.
Spliterator<E>	spliterator()	Creates a late-binding and fail-fast Spliterator over the elements in this list.
List<E>	subList(int fromIndex, int toIndex)	Returns a view of the portion of this List between fromIndex, inclusive, and toIndex, exclusive.
Object[]	toArray()	Returns an array containing all of the elements in this Vector in the correct order.
<T> T[]	toArray(T[] a)	Returns an array containing all of the elements in this Vector in the correct order; the runtime type of the returned array is that of the specified array.
String	toString()	Returns a string representation of this Vector, containing the String representation of each element.
void	trimToSize()	Trims the capacity of this vector to be the vector's current size.

Methods declared in class Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Modifier and Type	Method	Description
protected void	finalize()	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
final Class<?>	getClass()	Returns the runtime class of this Object.
final void	notify()	Wakes up a single thread that is waiting on this object's monitor.
final void	notifyAll()	Wakes up all threads that are waiting on this object's monitor.
final void	wait()	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
final void	wait(long timeoutMillis)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
final void	wait(long timeoutMillis, int nanos)	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Methods declared in interface Collection

parallelStream, stream, toArray

Modifier and Type	Method	Description
default Stream<E>	parallelStream()	Returns a possibly parallel Stream with this collection as its source.
default Stream<E>	stream()	Returns a sequential Stream with this collection as its source.
default <T> T[]	toArray(IntFunction<T[]> generator)	Returns an array containing all of the elements in this collection, using the provided generator function to allocate the returned array.

Methods declared in interface List

addFirst, addLast, getFirst, getLast, removeFirst, removeLast, reversed, sort

Modifier and Type	Method	Description
default void	addFirst(E e)	Adds an element as the first element of this collection (optional operation).
default void	addLast(E e)	Adds an element as the last element of this collection (optional operation).
default E	getFirst()	Gets the first element of this collection.
default E	getLast()	Gets the last element of this collection.
default E	removeFirst()	Removes and returns the first element of this collection (optional operation).
default E	removeLast()	Removes and returns the last element of this collection (optional operation).
default List<E>	reversed()	Returns a reverse-ordered view of this collection.
default void	sort(Comparator<? super E> c)	Sorts this list according to the order induced by the specified Comparator (optional operation).

Constructor Details

Stack

public Stack()

Creates an empty Stack.

Method Details

push

public E push(E item)

Pushes an item onto the top of this stack. This has exactly the same effect as:

addElement(item)

Parameters:

item - the item to be pushed onto this stack.

Returns:

the item argument.

See Also:

• Vector.addElement(E)

pop

public E pop()

Removes the object at the top of this stack and returns that object as the value of this function.

Returns:

The object at the top of this stack (the last item of the Vector object).

Throws:

EmptyStackException - if this stack is empty.

peek

public E peek()

Looks at the object at the top of this stack without removing it from the stack.

Returns:

the object at the top of this stack (the last item of the Vector object).

Throws:

EmptyStackException - if this stack is empty.

empty

public boolean empty()

Tests if this stack is empty.

Returns:

true if and only if this stack contains no items; false otherwise.

search

public int search(Object o)

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.

Parameters:

o - the desired object.

Returns:

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.