Katbin

class ArrayStack {

    // note: variable declarations
    private int capacity; // note: max length of array
    private int top = 0; // note: initialize a default value of top
    private String[] storage; // note: array is of string values

    // note: constructor = initialize an object instance of the class
    public ArrayStack(int size) {
        // todo: pass the value of size to capacity
        storage = new String[size]; // todo: update the array capacity
    }

    // note: will display the array
    public void show() {
        // note: the top of the stack starts from array[0] then newer item gets added on top of another until it reaches its capacity limit
        for (int i = capacity - 1; i >= 0; i--) {
            /* note: should print like this: 
            stack[9]   = 10th value
            stack[8]   = 9th value
            stack[7]   = 8rd value
            ....  
            stack[1]   = 2nd value
            stack[0]   = 1st value
            */
        }
        System.out.println(); // note: prints optional new line for readability
    }

    // note: will check if it's true that the array is empty
    private boolean isEmpty() {
        if (storage[0] == null) { // note: compares if index[0] or top is null or empty
            System.out.println(" "); // todo: print error message here
            System.out.println(); // note: this prints optional new line for readability
            return true;
        }
        return false; // note: defaults to false
    }

    // note: will check if it's true that the array is full
    private boolean isFull() {
        if (top == capacity) { // note: compares if top has reached capacity limit
            System.out.println(" "); // todo: print error message here
            return true;
        }
        return false; // note: defaults to false
    }

    // note: will add value to the array
    public void push(String value) {
        System.out.println("... trying to push on stack[" + top + "] ...");
        if (isFull()) {
            System.out.println(" "); // todo: print error message here
            System.out.println(); // note: prints optional new line for readability
        } else {
            storage[top] = value;
            top++;
            System.out.println(value + " was successfully _________."); // todo: what does push do?
            System.out.println(); // prints optional new line for readability
        }
    }

    // note: will remove value to the array
    public void pop() {
        System.out.println("... trying to pop stack[" + (top - 1) + "] ...");
        if (isEmpty()) { // note: checks if empty, then stop
            System.out.println(" "); // print error message here
            System.out.println(); // prints optional new line for readability
        } else {
            storage[top] = null; // todo: empty the value of top
            top--;
            System.out.println(storage[top] + " was successfully _________."); // todo: what does pop do?
            System.out.println();
        }
    }

    // note: will show the topmost value of the array
    public void peek() {
        if (isEmpty()) {
            System.out.println("PEEK TOP = NULL");
            System.out.println();
        } else {
            System.out.println("PEEK TOP = " + storage[top]);
            System.out.println();
        }
    }

}

public class Main {

    public static void main(String[] args) {
        ArrayStack storage = new ArrayStack(10);
        // construct a new array queue and assign 10 as the integer value for the size limit of the stack
        System.out.println(storage);
        // show empty stack
        // try removing on an empty stack
        // peek top element of an empty stack
        storage.push("one");
        // show the updated stack
        // peek if top element is "one"
        storage.push("two");
        // show the updated stack
        // peek if top element is "two"
        storage.push("three");
        // show the updated stack
        // peek if top element is "three"
        storage.push("four");
        // show the updated stack
        storage.push("five");
        // show the updated stack
        // try removing "five"
        storage.push("six");
        storage.push("seven");
        storage.push("eight");
        storage.push("nine");
        storage.push("ten");
        // show the updated stack
        // peek if top element is "ten"
        // try adding "eleven"
        // try adding "twelve"
        // show the updated stack
    }
}

// Credit to https://github.com/deepak-malik/Data-Structures-In-Java/blob/master/src/com/deepak/data/structures/Stack/ArrayBasedStack.java