106 lines
2.4 KiB
Java
106 lines
2.4 KiB
Java
package DataStructures.Stacks;
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import java.util.ArrayList;
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import java.util.EmptyStackException;
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/**
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* This class implements a Stack using an ArrayList.
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*
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* <p>A stack is exactly what it sounds like. An element gets added to the top of the stack and only
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* the element on the top may be removed.
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*
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* <p>This is an ArrayList Implementation of a stack, where size is not a problem we can extend the
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* stack as much as we want.
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*/
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public class StackArrayList {
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/** Driver Code */
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public static void main(String[] args) {
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StackArrayList stack = new StackArrayList();
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assert stack.isEmpty();
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for (int i = 1; i <= 5; ++i) {
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stack.push(i);
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assert stack.size() == i;
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}
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assert stack.size() == 5;
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assert stack.peek() == 5 && stack.pop() == 5 && stack.peek() == 4;
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/* pop elements at the top of this stack one by one */
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while (!stack.isEmpty()) {
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stack.pop();
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}
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assert stack.isEmpty();
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try {
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stack.pop();
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assert false; /* this should not happen */
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} catch (EmptyStackException e) {
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assert true; /* this should happen */
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}
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}
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/** ArrayList representation of the stack */
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private ArrayList<Integer> stack;
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/** Constructor */
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public StackArrayList() {
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stack = new ArrayList<>();
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}
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/**
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* Adds value to the end of list which is the top for stack
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*
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* @param value value to be added
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*/
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public void push(int value) {
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stack.add(value);
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}
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/**
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* Removes the element at the top of this stack and returns
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*
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* @return Element popped
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* @throws EmptyStackException if the stack is empty.
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*/
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public int pop() {
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if (isEmpty()) {
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throw new EmptyStackException();
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}
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/* remove the element on the top of the stack */
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return stack.remove(stack.size() - 1);
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}
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/**
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* Test if the stack is empty.
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*
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* @return {@code true} if this stack is empty, {@code false} otherwise.
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*/
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public boolean isEmpty() {
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return stack.isEmpty();
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}
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/**
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* Return the element at the top of this stack without removing it from the stack.
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*
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* @return the element at the top of this stack.
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*/
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public int peek() {
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if (isEmpty()) {
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throw new EmptyStackException();
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}
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return stack.get(stack.size() - 1);
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}
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/**
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* Return size of this stack.
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*
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* @return size of this stack.
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*/
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public int size() {
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return stack.size();
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}
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}
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