153 lines
4.1 KiB
Java
153 lines
4.1 KiB
Java
/**
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* This class implements a Stack using a regular array.
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* <p>
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* A stack is exactly what it sounds like. An element gets added to the top of
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* the stack and only the element on the top may be removed. This is an example
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* of an array implementation of a Stack. So an element can only be added/removed
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* from the end of the array. In theory stack have no fixed size, but with an
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* array implementation it does.
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*
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* @author Unknown
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*/
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public class StackArray {
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/**
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* Main method
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*
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* @param args Command line arguments
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*/
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public static void main(String[] args) {
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// Declare a stack of maximum size 4
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StackArray myStackArray = new StackArray(4);
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// Populate the stack
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myStackArray.push(5);
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myStackArray.push(8);
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myStackArray.push(2);
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myStackArray.push(9);
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System.out.println("*********************Stack Array Implementation*********************");
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System.out.println(myStackArray.isEmpty()); // will print false
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System.out.println(myStackArray.isFull()); // will print true
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System.out.println(myStackArray.peek()); // will print 9
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System.out.println(myStackArray.pop()); // will print 9
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System.out.println(myStackArray.peek()); // will print 2
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}
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/**
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* The max size of the Stack
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*/
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private int maxSize;
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/**
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* The array representation of the Stack
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*/
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private int[] stackArray;
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/**
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* The top of the stack
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*/
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private int top;
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/**
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* Constructor
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*
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* @param size Size of the Stack
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*/
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public StackArray(int size) {
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maxSize = size;
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stackArray = new int[maxSize];
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top = -1;
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}
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/**
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* Adds an element to the top of the stack
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*
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* @param value The element added
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*/
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public void push(int value) {
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if (!isFull()) { // Checks for a full stack
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top++;
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stackArray[top] = value;
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} else {
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resize(maxSize * 2);
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push(value); // don't forget push after resizing
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}
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}
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/**
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* Removes the top element of the stack and returns the value you've removed
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*
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* @return value popped off the Stack
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*/
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public int pop() {
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if (!isEmpty()) { // Checks for an empty stack
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return stackArray[top--];
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}
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if (top < maxSize / 4) {
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resize(maxSize / 2);
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return pop();// don't forget pop after resizing
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} else {
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System.out.println("The stack is already empty");
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return -1;
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}
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}
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/**
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* Returns the element at the top of the stack
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*
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* @return element at the top of the stack
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*/
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public int peek() {
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if (!isEmpty()) { // Checks for an empty stack
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return stackArray[top];
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} else {
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System.out.println("The stack is empty, cant peek");
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return -1;
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}
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}
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private void resize(int newSize) {
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// private int[] transferArray = new int[newSize]; we can't put modifiers here !
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int[] transferArray = new int[newSize];
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// for(int i = 0; i < stackArray.length(); i++){ the length isn't a method .
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for (int i = 0; i < stackArray.length; i++) {
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transferArray[i] = stackArray[i];
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stackArray = transferArray;
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}
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maxSize = newSize;
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}
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/**
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* Returns true if the stack is empty
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*
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* @return true if the stack is empty
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*/
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public boolean isEmpty() {
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return (top == -1);
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}
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/**
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* Returns true if the stack is full
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*
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* @return true if the stack is full
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*/
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public boolean isFull() {
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return (top + 1 == maxSize);
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}
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/**
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* Deletes everything in the Stack
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* <p>
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* Doesn't delete elements in the array
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* but if you call push method after calling
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* makeEmpty it will overwrite previous
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* values
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*/
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public void makeEmpty() { // Doesn't delete elements in the array but if you call
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top = -1; // push method after calling makeEmpty it will overwrite previous values
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}
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}
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