A Cookie Helper object in JavaScript

This example is a little helper class to make and erase cookies in javascript. I will first post the Cookies.js script that will create, read, and erase cookies from your browser.

Cookies.js


/*
author: Copypasteearth 7/17/2017
*/

function COOKIE () {

this.createCookie = function (name,value,days) {
if (days) {
var date = new Date();
date.setTime(date.getTime()+(days*24*60*60*1000));
var expires = "; expires="+date.toGMTString();
}
else var expires = "";
document.cookie = name+"="+value+expires+"; path=/";
}
,
this.readCookie = function (name) {
var nameEQ = name + "=";
var ca = document.cookie.split(';');
for(var i=0;i < ca.length;i++) {
var c = ca[i];
while (c.charAt(0)==' ') c = c.substring(1,c.length);
if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
}
return null;
}
,
this.eraseCookie = function(name) {
this.createCookie(name,"",-1);
}
}

Then you just include this javascript in a webpage and create the object and then you can call the different functions as you will. Here is an example HTML file using it. This file just pretty much tests out the Cookies.js file.

index.html


<!DOCTYPE html>

<html lang="en">
<head>
<meta charset="utf-8" />
<title>profile</title>
</head>

<body>

<script src="Cookies.js"></script>
<h1>this is a test of Cookies</h1>
<h2 id = "cook"></h2>
<input id = "cookiename" type="text" placeholder="cookie name..."></input>
<input id = "cookievalue" type="text" placeholder="cookie value..."></input>
<input id = "days" type = "number" placeholder="number of days"></input>
<button onclick="buttonClick()">Create Cookie</button>
<br>
<input id = "getcookie" placeholder="cookie name"></input>
<button onclick="getCookie()">Read Cookie</button>
<br>
<input id = "erase" placeholder="cookie name"></input>
<button onclick="deleteCookie()">Erase Cookie</button>
<p id= "paragraph"></p>
<script>
var Cookie = new COOKIE();
function buttonClick(){
var name = document.getElementById("cookiename").value;
var value = document.getElementById("cookievalue").value;
var days = document.getElementById("days").value;
Cookie.createCookie(name,value,days);
document.getElementById("paragraph").innerText = "Cookie Created: " + name + "=" + value + ";" + days;
}
function getCookie(){
var name = document.getElementById("getcookie").value;
var cookie = Cookie.readCookie(name);
document.getElementById("paragraph").innerText = "Cookie Read: " + name + "=" + cookie;
}
function deleteCookie(){
var name = document.getElementById("erase").value;
Cookie.eraseCookie(name);
document.getElementById("paragraph").innerText = "Cookie Erased: " + name;
}
</script>
</body>

</html>

and that’s pretty much it for this article. Maybe you can get some use out of this. I hope you enjoyed this article.

QuickSort sorting algorithm in java with Generics that implement Comparable

In this article I’m going to touch on the sorting algorithm called Quicksort. Its worst case time complexity is O(n^2) and its best case time complexity is O(nlogn). Firstly the method we are going to make is going to take a generic array and those elements should implement the Comparable interface so they can be sorted. Take this Circle class for example. When you implement the Comparable interface you specify in the compareTomethod what makes a circle greater than, less than, or equal to another circle. In this example we return whether the radius of the circle is bigger or smaller than the circle it is being compared to.

Circle.java

/**
 * author: copypasteearth
 * date: 7/17/2019
 */
public class Circle implements Comparable<Circle> {
    public int xValue;
    public int yValue;
    public int radius;

@Override
public int compareTo(Circle o) {
return (this.radius - o.radius);
}
@Override
public String toString() {
return "x: " + xValue + " ---y: " + yValue + " ---radius: " + radius;
}
}

Next we create the Quicksort class that has the method quicksort and a main method to test out the quicksort method. The quicksort method is a recursive method and the base case is if(a < b). The method goes through the generic array and sorts the elements based on what the compareTo method tells it. Here is the Quicksort class.

Quicksort.java

/**
 * author: copypasteearth
 * date: 7/17/2019
 */
import java.util.Random;
public class QuickSort<T extends Comparable<T>> {

public static <T extends Comparable<T>> void quicksort(T[] array, int a, int b) {
if (a < b) {
int i = a, j = b;
T x = array[(i + j) / 2];

do {
while (array[i].compareTo(x) < 0) i++;
while (x.compareTo(array[j]) < 0) j--;

if ( i <= j) {
T tmp = array[i];
array[i] = array[j];
array[j] = tmp;
i++;
j--;
}

} while (i <= j);

quicksort(array, a, j);
quicksort(array, i, b);
}
}

public static void main(String[] args) {
Integer[] integerarray = {50, 55, 11, 89, 90, 1, 20, 11};
QuickSort<Integer> qsinteger = new QuickSort<Integer>();
qsinteger.quicksort(integerarray, 0, integerarray.length-1);
for(Integer i: integerarray) {
System.out.println(i);
}
String[] stringarray = {"bird","moth","apple","zebra","banana","desert","pig"};
QuickSort<String> qsstring = new QuickSort<String>();
qsstring.quicksort(stringarray, 0, stringarray.length-1);
for(String i: stringarray) {
System.out.println(i);
}
Circle[] circlearray = new Circle[20];
Random rand = new Random();
for (int index = 0; index < 20; index++)
{
circlearray[index] = new Circle();
circlearray[index].xValue = Math.abs(rand.nextInt()) % 100;
circlearray[index].yValue = Math.abs(rand.nextInt()) % 100;
circlearray[index].radius = Math.abs(rand.nextInt()) % 100;

}
System.out.println("Circle Array Unsorted....");
for(int i = 0;i < 20;i++){

System.out.println(circlearray[i]);
}
QuickSort<Circle> qscircle = new QuickSort<Circle>();
qscircle.quicksort(circlearray, 0, circlearray.length-1);
System.out.println("Circle Array Sorted");
for(Circle i: circlearray) {
System.out.println(i);
}

}

}

If you run this code you will see the results from the main method. First it sorts an Integer array and then a String array. Then it makes a Circle array and prints them out unsorted then it sorts them and then prints them out again sorted. That pretty much does it for this example on quicksorting. In the future I will probably go through the rest of the sorting algorithms. Hope you enjoyed it.

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Obesity in the World Today

Obesity is a growing problem in today’s world.  You might ask what are the reasons that today’s people are more likely to be obese. People try to cut carbohydrates, sugar, fat, anything to live a healthier life these days and they feel even more pressured to do so because of the increasing epidemic of obesity.  There are a lot of factors that can contribute to a person being obese which are diet and exercise.  Through the right diet and exercise a person will not even have to worry about obesity.

Being on a diet is important because everyone is on one.  If you weren’t on a diet you would be dead from starvation.  Everyone is different having to do with genetics and how they are affected by the environment. Culture is another factor that has a lot to do with diet.  Some people cannot eat sugar and are diabetics and sugar intake has increased at an order of magnitude or even higher since the 80’s when I was a kid.  Everything has sugar in it these days and is probably the main culprit in the obesity craze.  Regulating sugar intake is probably important so you don’t eventually become diabetic.  Some people say that cutting carbohydrates is a good way to battle obesity.  Why are companies packing their foods with sugar?  Because sugar tastes good and it is an inborn preference to love the sweet mother’s milk when a child is just born.  Whether companies took advantage of this innate preference is besides the point that people really need to watch their diets so that they do not run into health problems like obesity.  Some people can eat all of the junk food they want and not gain a pound.  I know this because I am one of those people.  But since I’ve been getting older I have started to watch my diet because cholesterol is really building up inside me.  So everyone is on a diet and the point is that you have to be aware of your diet and change it so you can stay healthy.

Exercise these days seems to be a thing of the past.  When I was young back in the 1980’s I was outside at the parks every day running around, wading through the creek, and building tree forts.  These days the kids want to not even move and look at their tablets and smart devices.  You probably don’t burn a lot of calories when you don’t even move.  Exercise is important for everyday functioning.  I recently read an article that said your memory improves when you exercise because it enlarges your hippocampus, the area of your brain that is used for memory.  So exercise enlarges your brain and burns calories.  Calories left over at the end of the day turn to fat when you sleep.  I cannot urge it enough these days that the kids need to exercise in order to stay healthy.  I always take my nieces to the park so they can run around and play with other kids and get out some of the energy that they have from calories in the food they eat.  I used to run 5 miles at once, once a week and I am going to try to start it up again to lower my cholesterol.  Exercising will lead to having a faster metabolism.  The faster your metabolism the quicker you will burn calories and fat.  If you have a fast metabolism you would never even have to worry about obesity, ever.

To conclude I’d like to again stress the effects of diet and exercise on the disease of obesity that has struck our country in the past couple decades.  As far as diet is concerned watch how much sugar, carbohydrates, fats, and calories you take in.  And for exercise, make sure you go out regularly and stay active so you can burn all those calories and speed up your metabolism.  Being healthy requires a proper diet and exercise regimen to stay clear of obesity.

How to make a mouse maze in Java

This is the code to make a mouse maze with recursion using a stack and a list with a GUI in Java.

First we will make a Mouse class

Mouse.java

import java.util.ArrayList;
import java.util.List;
import java.util.Stack;

public class Mouse {
public int x,y;
public Stack<Coordinate> decisions;
public List<Coordinate> solution;

public Mouse(int x, int y){
this.x = x;
this.y = y;
decisions = new Stack<Coordinate>();
solution = new ArrayList<Coordinate>();
}
}

Then we will make the coordinate class

Coordinate.java

public class Coordinate {
public int x,y;

public Coordinate(int x,int y){
this.x = x;
this.y = y;
}

@Override
public boolean equals(Object obj) {

boolean sameSame = false;
if (obj != null && obj instanceof Coordinate)
{
if(this.x == ((Coordinate)obj).x && this.y == ((Coordinate)obj).y){
sameSame = true;
}

}
return sameSame;
}
}

Now its time for the decision class

Decision.java

public class Decision {

public boolean up,down,left,right;
public int x,y;
public Decision(int x, int y){
up = down = left = right = false;
this.x = x;
this.y = y;
}
public Decision(boolean up,boolean down,boolean right,boolean left){
this.up = up;
this.down = down;
this.right = right;
this.left = left;
}
public void setLeft(boolean left){
this.left = left;
}
public void setRight(boolean right){
this.right = right;
}
public void setUp(boolean up){
this.up = up;
}
public void setDown(boolean down){
this.down = down;
}
@Override
public String toString() {
// TODO Auto-generated method stub
return x + " x -- y " + y;
}

}

Now we have to make the maze class which does most of the hard work

Maze.java

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Rectangle;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.JComponent;

public class Maze extends JComponent{
public char[][] maze = null;
public Rectangle[][] rects = null;
public boolean mousebool = false;
public boolean backtrack = false;
public Mouse mouse;
public Random random = new Random();
public Coordinate startingPoint;
public boolean first = true;
public boolean solv = true;
public int lastx,lasty;
public String navigation = "working!!!";

@Override
protected void paintComponent(Graphics g) {
super.paintComponent(g);

if(maze != null){
for(int i = 0;i < maze.length;i++){
for(int j = 0;j < maze[0].length;j++){
if(maze[i][j] == '1'){
g.setColor(Color.BLACK);
g.fillRect(rects[i][j].x, rects[i][j].y, rects[i][j].width, rects[i][j].height);
g.setColor(Color.WHITE);
g.drawRect(rects[i][j].x, rects[i][j].y, rects[i][j].width, rects[i][j].height);
}else if(maze[i][j] == '0'){
g.setColor(Color.white);
g.fillRect(rects[i][j].x, rects[i][j].y, rects[i][j].width, rects[i][j].height);
g.setColor(Color.BLACK);
g.drawRect(rects[i][j].x, rects[i][j].y, rects[i][j].width, rects[i][j].height);
}
}
}
if(mousebool){
g.setColor(Color.PINK);

g.fillOval(rects[mouse.x][mouse.y].x, rects[mouse.x][mouse.y].y, rects[mouse.x][mouse.y].width, rects[mouse.x][mouse.y].height);
}
}

}
public void setMaze(char[][] maze){
mousebool = false;
this.maze = maze;
rects = new Rectangle[maze.length][maze[0].length];
for(int i = 0;i < rects.length;i++){
for(int j = 0;j < rects[0].length;j++){
rects[i][j] = new Rectangle(i * (getWidth()/rects.length),j * (getHeight()/rects[0].length)
,getWidth()/rects.length,getHeight()/rects[0].length);
}
}
repaint();
}
public void setMouse(int x,int y){
mousebool = true;
mouse = new Mouse(x,y);
startingPoint = new Coordinate(x,y);
mouse.solution.add(new Coordinate(x,y));
mouse.decisions.push(new Coordinate(x,y));
first = true;

repaint();
}
public void solve(){

if(mouse.x > 0 && mouse.x < maze.length - 1 && mouse.y > 0 && mouse.y < maze[0].length - 1 && mouse.decisions.size() > 0){

//System.out.println(wasHere(coord) + "now");
//north
System.out.println(wasHere(new Coordinate(mouse.x,mouse.y - 1)) + "north");
if (!(maze[mouse.x][mouse.y - 1] == '1') && !wasHere(new Coordinate(mouse.x,mouse.y - 1))) mouse.decisions.push(new Coordinate(mouse.x,mouse.y - 1));
//east
System.out.println(wasHere(new Coordinate(mouse.x + 1,mouse.y)) + "east");
if (!(maze[mouse.x + 1][mouse.y] == '1') && !wasHere(new Coordinate(mouse.x + 1,mouse.y))) mouse.decisions.push(new Coordinate(mouse.x + 1,mouse.y));
//west
if (!(maze[mouse.x - 1][mouse.y] == '1') && !wasHere(new Coordinate(mouse.x - 1,mouse.y))) mouse.decisions.push(new Coordinate(mouse.x - 1,mouse.y));
//south
if(!(maze[mouse.x][mouse.y + 1] == '1') && !wasHere(new Coordinate(mouse.x,mouse.y + 1))) mouse.decisions.push(new Coordinate(mouse.x,mouse.y + 1));

Coordinate coord = mouse.decisions.pop();

mouse.x = coord.x;
mouse.y = coord.y;

mouse.solution.add(coord);

ActionListener taskPerformer = new ActionListener() {

@Override
public void actionPerformed(ActionEvent arg0) {
solve();

}
};
javax.swing.Timer t = new javax.swing.Timer( 250, taskPerformer);
t.setRepeats(false);
t.start();
//solve();

repaint();
}else{
solv = false;
if(mouse.decisions.size() == 0){
mouse.solution.clear();
navigation = "there is no solution";
}else{
mouse.solution.clear();
findPath(startingPoint.x,startingPoint.y);
navigation = "maze complete";
}
}

//solve();
}
public boolean findPath(int x,int y){
if(x < 0 || y < 0 || x > maze.length - 1 || y > maze[0].length - 1)return false;

if(!(x > 0 && x < maze.length - 1 && y > 0 && y < maze[0].length - 1) && maze[x][y] == '0')
{
mouse.solution.add(new Coordinate(x,y));
return true;// && maze[x][y] == '0') return true;//&& maze[x][y] == '0') return true;
}
if(maze[x][y] == '1') return false;

mouse.solution.add(new Coordinate(x,y));
if(!mouse.solution.contains(new Coordinate(x,y - 1)))
if(findPath(x,y-1) == true) return true;
if(!mouse.solution.contains(new Coordinate(x+1,y)))
if(findPath(x + 1,y) == true) return true;
if(!mouse.solution.contains(new Coordinate(x,y+1)))
if(findPath(x,y + 1)== true) return true;
if(!mouse.solution.contains(new Coordinate(x-1,y)))
if(findPath(x - 1,y)== true) return true;
mouse.solution.remove(new Coordinate(x,y));
return false;
}

public boolean wasHere(Coordinate coord){
return mouse.solution.contains(coord);
}
public void TraverseMouse(int x){
if(x < mouse.solution.size()){
Coordinate coord = mouse.solution.get(x);
mouse.x = coord.x;
mouse.y = coord.y;
final int xt = x+=1;
ActionListener taskPerformer = new ActionListener() {

@Override
public void actionPerformed(ActionEvent arg0) {
TraverseMouse(xt);

}
};
javax.swing.Timer t = new javax.swing.Timer( 250, taskPerformer);
t.setRepeats(false);
t.start();
}
repaint();

}
public String Navigation(){
return navigation;
}
}

And finally the Main class to make the GUI

Main.java

import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.filechooser.FileNameExtensionFilter;

public class Main {
public static int width;
public static int height;
public static char[][] maze1;
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}catch(Exception ex) {
ex.printStackTrace();
}

SwingUtilities.invokeLater(new Runnable() {
public void run() {
create();
}
});

}
public static void create(){
JFrame frame = new JFrame("Mouse Maze");
final Maze maze = new Maze();
frame.setSize(500, 500);
frame.setLocation((int)(Toolkit.getDefaultToolkit().getScreenSize().getWidth()/2)-264,
(int)(Toolkit.getDefaultToolkit().getScreenSize().getHeight()/2)-330);
maze.setSize(400, 400);
Container content = frame.getContentPane();
//Creates a new container
content.setLayout(new BorderLayout());

frame.add(maze,BorderLayout.CENTER);
//frame.add(maze);
JPanel panel = new JPanel(new BorderLayout());
JPanel panel1 = new JPanel(new BorderLayout());
JPanel panel2 = new JPanel(new BorderLayout());
JPanel finish = new JPanel(new BorderLayout());
final JLabel textFile = new JLabel(" ex: maze.txt ");
JButton pickFile = new JButton("Pick file");
pickFile.addActionListener(new ActionListener(){

@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
JFileChooser chooser = new JFileChooser();
FileNameExtensionFilter filter = new FileNameExtensionFilter(
".txt file", "txt");
chooser.setFileFilter(filter);

int returnVal = chooser.showOpenDialog(null);
if(returnVal == JFileChooser.APPROVE_OPTION) {
try {
BufferedReader read = new BufferedReader(new FileReader(chooser.getSelectedFile()));
String rea = read.readLine();
String[] split = rea.split(" ");
width = Integer.valueOf(split[0]);
height = Integer.valueOf(split[1]);

String readline;
int num = 0;
maze1 = new char[width][height];
while((readline = read.readLine()) != null){
char[] ch = readline.toCharArray();
for(int i = 0;i < ch.length;i++){
maze1[i][num] = ch[i];
}
num++;
}
maze.setMaze(maze1);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
textFile.setText(chooser.getSelectedFile().getName());
}else{

}
}

});

panel.add(pickFile,BorderLayout.CENTER);
panel.add(textFile,BorderLayout.WEST);
JButton setMouse = new JButton("Set Mouse");
final JTextField mouseText = new JTextField("x,y",15);
JButton solve = new JButton("SOLVE");
JButton traverse = new JButton("TRAVERSE");
final JLabel error = new JLabel("ERROR MESSAGES!!!!");
panel2.add(solve,BorderLayout.NORTH);
panel2.add(traverse,BorderLayout.CENTER);
panel2.add(error,BorderLayout.SOUTH);
panel1.add(setMouse,BorderLayout.CENTER);
panel1.add(mouseText,BorderLayout.WEST);
finish.add(panel,BorderLayout.NORTH);
finish.add(panel1,BorderLayout.CENTER);
finish.add(panel2,BorderLayout.SOUTH);
//content.setLayout(new BorderLayout());
content.add(finish, BorderLayout.SOUTH);
traverse.addActionListener(new ActionListener(){

@Override
public void actionPerformed(ActionEvent e) {
// TODO Auto-generated method stub
maze.TraverseMouse(0);
}

});
solve.addActionListener(new ActionListener(){

@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub

maze.solve();

error.setText(maze.navigation);

}

});
setMouse.addActionListener(new ActionListener(){

@Override
public void actionPerformed(ActionEvent arg0) {
String mousePosition = mouseText.getText();
String[] splitposition = mousePosition.split(",");
try{
int x = Integer.valueOf(splitposition[0]);
int y = Integer.valueOf(splitposition[1]);
if(x >= width || y >= height){
error.setText("those coordinates are not in range of your maze, try again, 0-"+ (width - 1)+",0-"+(height-1));
}else if(maze1[x][y] == '1'){
error.setText("you cannot place the mouse on a wall, try again");
}else{
maze.setMouse(x, y);
error.setText("coordinates set.");
}
}catch(NumberFormatException e){
error.setText("You Must enter the mouse position \"x,y\" example: 10,20");
}catch(ArrayIndexOutOfBoundsException e){
e.printStackTrace();
error.setText("You Must enter the mouse position \"x,y\" example: 10,20");
}

}

});

//frame.add(panel);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//makes it so you can close
frame.setVisible(true);
//char[][] ch = new char[][]{{'1','1','1','1'},{'1','0','0','1'},{'1','0','0','1'},{'1','1','1','1'}};
//maze.setMaze(ch);
}

}

You will have to use a text file in this format where a 1 is a wall and a 0 is part of the path remember .txt file the first line means 10 width and 5 height for the maze


10 5
1111111111
1010001111
1011011111
1011000011
1111111111

You can try it and alter it to your own code, thanks for reading.

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Genie Lamp Free a silly app for android!!!

Genie Lamp Free is a funny voice recognition app where you rub the lamp and make a wish to a genie and the genie gives a reply based on what you say.  The app has over 5,000 downloads on google play store. Genie Lamp Free is where you can go to try the game. Its awesome because its free and you might get a few kicks out of it.

So go download GenieLampFree and leave a review for the developer jacs@pps on google play store.  As far as I know its the only genie in a lamp app that you can actually talk to.  They have a lot of great apps on there who knows what those guys are up to. The app is just for entertainment purposes and only available for android devices so I guess that’s too bad for all the apple gurus out there. Thanks for reading and go download that app. 😉

Excalibur Strength is awesome!!!

This post is about a game that is available on the Play Store and it is free with in app purchases.  The game is called Excalibur Strength and you can get it here Link to Excalibur Strength Presently the game has 4 and a half stars but I personally give it a 5.  The story behind the game is that the sword, Excalibur by it self is in the afterlife and it has to fend off all of the envious souls that couldn’t lift the sword from the stone in life and that is where Excalibur gets the strength and why it is known as one of the most powerfull weapons in the universe.  Excalibur Strength is a classic hoard game with unlimited waves. The game has 7 special moves and the monetary system is bones. You can use bones to unlock new weapons and special features.  You can unlock the whole game for a purchase of 20 dollars worth of bones, or you can just play the game until you have earned enough bones to unlock what youd like.  Personally I love the back story of the game about envious souls and the strength of Excalibur being derived from eternally battling the souls.  Its a decent game with pretty good graphics and audio.  The audio is very good, you can switch between 3 different songs to play while your playing.  So go download the game and rate it. Its only for android and it is a great all around action game. You’ll love it.

How to Implement a Stack in Java

If you are a computer science major when you take Data Structures and Algorithms you are going to have to learn about a Stack.  Java has a built in Stack class that you can use so you would probably never have to implement your own. In this example we will start with the Stack interface to formally define how our stack will be implemented.

Stack.java


/**
*
* @author Copypasteearth
*interface for the Stack implementation
* @param <T>
* generic parameter T
*/
public interface Stack<T>
{
/*
* push element onto the top of the stack
* @element
* the item to be pushed onto the top of the stack
*
*/
public void push(T element);
/**
* removes the top element from the stack and returns it
* @throws
* throws stackunderflowexception if the stack is empty
* @return
* returns T element
*/
public T pop();
/**
* lets you see the current top element of the stack without removing it
* @throws
* throws stackunderflowexception if the stack is empty
* @return
* returns T element (the top of the stack)
*/
public T top();
/**
* checks to see if the stack is empty
* @return
* returns true if the stack is empty, false otherwise
*/
public boolean isEmpty();
/**
* gets the size of the stack
* @return
* returns an integer representing how many items are on the stack
*/
public int getSize();

}

Next we will need a class that holds our information so we define the Node class to hold the data and a reference to the next Node in the stack.

Node.java


/**
*
* @author Copypasteearth
* Node class used to dynamically keep track of
* elements on the stack
*/
public class Node<T> {

/** holds the reference to Object of the node*/
public T data;
/** holds the reference to next node of the stack*/
public Node<T> next;
/**
*
* @param element
* element to be placed in data variable of Node
* @param next
* Node to be placed in next variable of Node
*/
public Node(T element,Node<T> next) {

this.data = element;
this.next = next;

}

}

Now we will define an Exception just incase someone trys to access the top of the stack and it is empty.

StackUnderflowException.java


/**
*
* @author Copypasteearth
* StackUnderflowException to be thrown when the
* stack tries to perform a getter method on an empty stack
*/
public class StackUnderflowException extends RuntimeException {

public StackUnderflowException() {
super();
// TODO Auto-generated constructor stub
}

public StackUnderflowException(String arg0) {
super(arg0);
// TODO Auto-generated constructor stub
}

public StackUnderflowException(Throwable arg0) {
super(arg0);
// TODO Auto-generated constructor stub
}

public StackUnderflowException(String arg0, Throwable arg1) {
super(arg0, arg1);
// TODO Auto-generated constructor stub
}

public StackUnderflowException(String arg0, Throwable arg1, boolean arg2,
boolean arg3) {
super(arg0, arg1, arg2, arg3);
// TODO Auto-generated constructor stub
}

}

And finally here is the implementation of the Stack interface, in a class called UnboundedStackImplementation.

UnboundedStackImplementation.java


/**
* @author Copypasteearth
*
* UnboundedStackImplementation is the version of a Stack
* created with the Stack interface dynamically creating
* instances of Node class to keep references to elements
* in the stack
*/
public class UnboundedStackImplementation<T> implements Stack<T> {

/** the count of how many elements are in the stack */
private int count;
/** the reference to the element on the top of the stack */
private Node<T> top;

/**
* constructor sets values of top and count and returns an
* instance of UnboundedStackImplementation
*/
public UnboundedStackImplementation()
{
this.count = 0;
this.top = null;
}

/*
* push element onto the top of the stack
* @element
* the item to be pushed onto the top of the stack
*
*/
@Override
public void push(T element) {

//create new node with element as data and top as next
Node<T> currentNode = new Node<T>(element,top);
//set top to the new node
top = currentNode;
//increment count
count++;


}

/**
* removes the top element from the stack and returns it
* @throws
* throws stackunderflowexception if the stack is empty
* @return
* returns T element
*/
@Override
public T pop() {
//get T with top method, may throw StackUnderflowException
T result = top();
//set top data to null
top.data = null;
//set top to the top next node
top = top.next;
//decrement count
count--;
return result;

}

/**
* lets you see the current top element of the stack without removing it
* @throws
* throws stackunderflowexception if the stack is empty
* @return
* returns T element (the top of the stack)
*/
@Override
public T top() {

//prepare result T to be returned by top
T result = null;
// if stack is not empty
if(!isEmpty()){
//set result to top variable data
result = top.data;
}else{
// if stack is empty there is no data to be returned
throw new StackUnderflowException("StackUnderflowException -- The Stack is empty!!!");
}

return result;
}

/**
* checks to see if the stack is empty
* @return
* returns true if the stack is empty, false otherwise
*/
@Override
public boolean isEmpty() {
if(top == null)
return true;
else
return false;
}

/**
* gets the size of the stack
* @return
* returns an integer representing how many items are on the stack
*/
@Override
public int getSize() {

return count;
}

}

And that’s it, I hope you appreciate this little demonstration about the data structure that is very commonly used in practice.  There are a ton of different data structures to choose from and some are better in certain situations than others.

Which is better for WebVR, ReactVR or Three.js

So I been doing a little research on some WebVR which is the new virtual reality API for Web Sites.  So far I think I like Three.js tools for WebVR better than ReactVR. The first thing that got me was the issues with ReactVR like not being able to use the VR mode in chrome for android, and another issue is when I installed the sample and hit the VR mode button then exit VR mode the button still says Exit VR and you cannot go back into VR mode unless you refresh the page, which is really bad to me.  So having done this research id say that Three.js is more consistent so far and ReactVR uses Three.js in their whole code so I give it to ReactVR for trying to simplify things but Three.js implementation and examples got them beat by far.

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