added in API level 1

Summary: Inherited Fields | Ctors | Methods | Inherited Methods | [Expand All]

Stack

public class Stack
extends Vector<E>

java.lang.Object
↳	java.util.AbstractCollection<E>
	↳	java.util.AbstractList<E>
		↳	java.util.Vector<E>
			↳	java.util.Stack<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>();

Summary

Inherited fields

From class


    java.util.Vector

From class


    java.util.AbstractList

Public constructors
`Stack()` Creates an empty Stack.

Public methods
`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.

Inherited methods

From class


  
    java.util.Vector

`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)`
`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(int index)` Returns a list iterator over the elements in this list (in proper sequence), starting at the specified position in the list.
`ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence).
`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.
`E`	`remove(int index)` Removes the element at the specified position in this Vector.
`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.
`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.
`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.
`void`	`sort(Comparator<? super E> c)` Sorts this list according to the order induced by the specified `Comparator`.
`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.

From class


  
    java.util.AbstractList

`void`	`add(int index, E element)` Inserts the specified element at the specified position in this list (optional operation). This implementation always throws an `UnsupportedOperationException`.
`boolean`	`add(E e)` Appends the specified element to the end of this list (optional operation).
`boolean`	`addAll(int index, Collection<? extends E> c)` Inserts all of the elements in the specified collection into this list at the specified position (optional operation). This implementation gets an iterator over the specified collection and iterates over it, inserting the elements obtained from the iterator into this list at the appropriate position, one at a time, using `add(int, E)`.
`void`	`clear()` Removes all of the elements from this list (optional operation).
`boolean`	`equals(Object o)` Compares the specified object with this list for equality.
`abstract E`	`get(int index)` Returns the element at the specified position in this list.
`int`	`hashCode()` Returns the hash code value for this list.
`int`	`indexOf(Object o)` Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. This implementation first gets a list iterator (with `listIterator()`).
`Iterator<E>`	`iterator()` Returns an iterator over the elements in this list in proper sequence.
`int`	`lastIndexOf(Object o)` Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element. This implementation first gets a list iterator that points to the end of the list (with `listIterator(size())`).
`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. This implementation returns a straightforward implementation of the `ListIterator` interface that extends the implementation of the `Iterator` interface returned by the `iterator()` method.
`ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence). This implementation returns `listIterator(0)`.
`E`	`remove(int index)` Removes the element at the specified position in this list (optional operation). This implementation always throws an `UnsupportedOperationException`.
`void`	`removeRange(int fromIndex, int toIndex)` Removes from this list all of the elements whose index is between `fromIndex`, inclusive, and `toIndex`, exclusive.
`E`	`set(int index, E element)` Replaces the element at the specified position in this list with the specified element (optional operation). This implementation always throws an `UnsupportedOperationException`.
`List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between the specified `fromIndex`, inclusive, and `toIndex`, exclusive. This implementation returns a list that subclasses `AbstractList`.

From class


  
    java.util.AbstractCollection

`boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation). This implementation always throws an `UnsupportedOperationException`.
`boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation). This implementation iterates over the specified collection, and adds each object returned by the iterator to this collection, in turn.
`void`	`clear()` Removes all of the elements from this collection (optional operation). This implementation iterates over this collection, removing each element using the `Iterator.remove` operation.
`boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element. This implementation iterates over the elements in the collection, checking each element in turn for equality with the specified element.
`boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection. This implementation iterates over the specified collection, checking each element returned by the iterator in turn to see if it's contained in this collection.
`boolean`	`isEmpty()` Returns `true` if this collection contains no elements. This implementation returns `size() == 0`.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements contained in this collection.
`boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation). This implementation iterates over the collection looking for the specified element.
`boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
`boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation). This implementation iterates over this collection, checking each element returned by the iterator in turn to see if it's contained in the specified collection.
`abstract int`	`size()` Returns the number of elements in this collection.
`<T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array. This implementation returns an array containing all the elements returned by this collection's iterator in the same order, stored in consecutive elements of the array, starting with index `0`.
`Object[]`	`toArray()` Returns an array containing all of the elements in this collection. This implementation returns an array containing all the elements returned by this collection's iterator, in the same order, stored in consecutive elements of the array, starting with index `0`.
`String`	`toString()` Returns a string representation of this collection.

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the 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.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

From interface


  
    java.util.List

`abstract boolean`	`add(E e)` Appends the specified element to the end of this list (optional operation).
`abstract void`	`add(int index, E element)` Inserts the specified element at the specified position in this list (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` Appends all of the elements in the specified collection to the end of this list, in the order that they are returned by the specified collection's iterator (optional operation).
`abstract boolean`	`addAll(int index, Collection<? extends E> c)` Inserts all of the elements in the specified collection into this list at the specified position (optional operation).
`abstract void`	`clear()` Removes all of the elements from this list (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this list contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this list contains all of the elements of the specified collection.
`abstract boolean`	`equals(Object o)` Compares the specified object with this list for equality.
`abstract E`	`get(int index)` Returns the element at the specified position in this list.
`abstract int`	`hashCode()` Returns the hash code value for this list.
`abstract int`	`indexOf(Object o)` Returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
`abstract boolean`	`isEmpty()` Returns `true` if this list contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this list in proper sequence.
`abstract int`	`lastIndexOf(Object o)` Returns the index of the last occurrence of the specified element in this list, or -1 if this list does not contain the element.
`abstract 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.
`abstract ListIterator<E>`	`listIterator()` Returns a list iterator over the elements in this list (in proper sequence).
`abstract E`	`remove(int index)` Removes the element at the specified position in this list (optional operation).
`abstract boolean`	`remove(Object o)` Removes the first occurrence of the specified element from this list, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes from this list all of its elements that are contained in the specified collection (optional operation).
`default void`	`replaceAll(UnaryOperator<E> operator)` Replaces each element of this list with the result of applying the operator to that element.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this list that are contained in the specified collection (optional operation).
`abstract E`	`set(int index, E element)` Replaces the element at the specified position in this list with the specified element (optional operation).
`abstract int`	`size()` Returns the number of elements in this list.
`default void`	`sort(Comparator<? super E> c)` Sorts this list according to the order induced by the specified `Comparator`.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this list.
`abstract List<E>`	`subList(int fromIndex, int toIndex)` Returns a view of the portion of this list between the specified `fromIndex`, inclusive, and `toIndex`, exclusive.
`abstract Object[]`	`toArray()` Returns an array containing all of the elements in this list in proper sequence (from first to last element).
`abstract <T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array is that of the specified array.

From interface


  
    java.util.Collection

`abstract boolean`	`add(E e)` Ensures that this collection contains the specified element (optional operation).
`abstract boolean`	`addAll(Collection<? extends E> c)` Adds all of the elements in the specified collection to this collection (optional operation).
`abstract void`	`clear()` Removes all of the elements from this collection (optional operation).
`abstract boolean`	`contains(Object o)` Returns `true` if this collection contains the specified element.
`abstract boolean`	`containsAll(Collection<?> c)` Returns `true` if this collection contains all of the elements in the specified collection.
`abstract boolean`	`equals(Object o)` Compares the specified object with this collection for equality.
`abstract int`	`hashCode()` Returns the hash code value for this collection.
`abstract boolean`	`isEmpty()` Returns `true` if this collection contains no elements.
`abstract Iterator<E>`	`iterator()` Returns an iterator over the elements in this collection.
`default Stream<E>`	`parallelStream()` Returns a possibly parallel `Stream` with this collection as its source.
`abstract boolean`	`remove(Object o)` Removes a single instance of the specified element from this collection, if it is present (optional operation).
`abstract boolean`	`removeAll(Collection<?> c)` Removes all of this collection's elements that are also contained in the specified collection (optional operation).
`default boolean`	`removeIf(Predicate<? super E> filter)` Removes all of the elements of this collection that satisfy the given predicate.
`abstract boolean`	`retainAll(Collection<?> c)` Retains only the elements in this collection that are contained in the specified collection (optional operation).
`abstract int`	`size()` Returns the number of elements in this collection.
`default Spliterator<E>`	`spliterator()` Creates a `Spliterator` over the elements in this collection.
`default Stream<E>`	`stream()` Returns a sequential `Stream` with this collection as its source.
`abstract <T> T[]`	`toArray(T[] a)` Returns an array containing all of the elements in this collection; the runtime type of the returned array is that of the specified array.
`abstract Object[]`	`toArray()` Returns an array containing all of the elements in this collection.

From interface


  
    java.lang.Iterable

Public constructors

Stack

added in API level 1

Stack ()

Creates an empty Stack.

Public methods

empty

added in API level 1

boolean empty ()

Tests if this stack is empty.

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

peek

added in API level 1

E peek ()

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

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

Throws
`EmptyStackException`	if this stack is empty.

pop

added in API level 1

E pop ()

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

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

Throws
`EmptyStackException`	if this stack is empty.

push

added in API level 1

E push (E item)

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

 addElement(item)

Parameters
`item`	`E`: the item to be pushed onto this stack.

Returns
`E`	the `item` argument.

See also:

addElement(E)

search

added in API level 1

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`	`Object`: the desired object.

Returns
`int`	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.

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