Class MyStack<E>

java.lang.Object

MyStack<E>

Type Parameters:

E - the type of elements in this list

public class MyStack<E>
extends Object

The MyStack class represents a last-in-first-out (LIFO) stack of objects. MyStack uses a generic ArrayList. Your stack should work exactly like java.util.Stack, except that you only have to implement a subset of the methods, as shown below.

Constructor Summary

Constructors

Constructor and Description
MyStack()

Method Summary

Modifier and Type	Method and Description
void	clear() Removes all the elements from the Stack.
boolean	contains(Object o) Returns true if this stack contains the specified element.
E	get(int index) Returns the element at the specified position in this list.
int	indexOf(Object o) Returns the index of the first occurrence of the specified element in this stack, or -1 if this ArrayList does not contain the element.
boolean	isEmpty() Test if Stack is empty
int	lastIndexOf(Object o) Returns the index of the last occurrence of the specified element in this stack, or -1 if this ArrayList does not contain the element.
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 item onto the top of this stack
int	search(Object o) Returns the 1-based position where an object is on this stack.
int	size() Returns the number of items in the stack
String	toString() String representation of a stack.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MyStack

public MyStack()

Method Detail

push

public E push(E item)

Pushes item onto the top of this stack

Parameters:

item - the item to be pushed onto this stack

Returns:

the item argument

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)

Throws:

EmptyStackException - if stack is empty when called

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)

Throws:

EmptyStackException - if stack is empty when called

isEmpty

public boolean isEmpty()

Test if Stack is empty

Returns:

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

size

public int size()

Returns the number of items in the stack

Returns:

size of the stack

clear

public void clear()

Removes all the elements from the Stack. The Stack will be empty after this call (unless an exception occurs)

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.

Example:

     s.push(4);
     s.push(5);
     s.push(6);
     s.search(6); // 1
     s.search(5); // 2
     s.search(4); // 3
     s.search(27) // -1
 

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.

contains

public boolean contains(Object o)

Returns true if this stack contains the specified element. More formally, returns true if and only if this stack contains at least one element e such that (o==null ? e==null : o.equals(e)).

Parameters:

o - element whose presence in this ArrayList is to be tested

Returns:

true if this ArrayList contains the specified element

indexOf

public int indexOf(Object o)

Returns the index of the first occurrence of the specified element in this stack, or -1 if this ArrayList does not contain the element. This is the index in the underlying ArrayList, NOT the position in the stack as defined in the search function. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Parameters:

o - element to search for

Returns:

the index of the first occurrence of the specified element in this ArrayList, or -1 if this ArrayList does not contain the element

lastIndexOf

public int lastIndexOf(Object o)

Returns the index of the last occurrence of the specified element in this stack, or -1 if this ArrayList does not contain the element. This is the index in the underlying ArrayList, NOT the position in the stack as defined in the search function. More formally, returns the highest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Parameters:

o - element to search for

Returns:

the index of the last occurrence of the specified element in this stack

toString

public String toString()

String representation of a stack.
Format is the same as AbstractCollection.toString() and the order is from bottom of the stack to the stop.

Overrides:

toString in class Object

Returns:

string representation of a stack

get

public E get(int index)

Returns the element at the specified position in this list.

Parameters:

index - index of the element to return. This is the index in the underlying ArrayList, NOT the position in the stack as defined in the search function.

Returns:

the element at the specified position in this list

Throws:

IndexOutOfBoundsException - if the index is out of range (index < 0 || index >= size())