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How to raise an int in a string in Java?

I am making a storybook and, because I'm not very creative with names, I gave images page numbers like so.
ImageIcon pg1icon = new ImageIcon("images/1.png");
ImageIcon pg2icon = new ImageIcon("images/2.png");
ImageIcon pg3icon = new ImageIcon("images/3.png");
JLabel pg1Label = new JLabel(pg1icon);
JLabel pg2Label = new JLabel(pg2icon);
JLabel pg3Label = new JLabel(pg3icon);
Because I have 30 pages, this process is getting tedious. Is there a way to scale the page num similar to i++?

Using streams we can handle this requirement concisely as:
List<JLabel> labels = IntStream.rangeClosed(1, 30)
.mapToObj(i -> new JLabel(new ImageIcon("images/" + i + ".png")))
.collect(Collectors.toList());

Assuming you only need the ImageIcon for the JLabel, you could use one array to store your thirty JLabel(s). Like,
int pageCount = 30;
JLabel[] labels = new JLabel[pageCount];
for (int i = 0; i < pageCount; i++) { // <-- i++ as requested
ImageIcon icon = new ImageIcon(String.format("images/%d.png", 1+i));
labels[i] = new JLabel(icon);
}
And then use labels[0] - labels[29] instead of pg1Label - pg30Label.

How to add parts of an image to an ArrayList - Java

For homework I am trying to add a sprite sheet to a 2D ArrayList for a simple card game. I want to be able to have it like you would in a normal 2D array only with the dynamic ability of the array list since I will have to remove cards that are already drawn.
I am using a number generator that will generate numbers between the first and last indexes (0 - 51) inclusive and it will show a card up on the screen when the user clicks the draw card button. Then it will allow another user or an AI to draw a card and it will determine who has the highest card and declare that person the winner of that round, remove both drawn cards and repeat the cycle until 26 turns have been surpassed then the program will tally up all round wins and the player with the most round wins wins the game overall.
My question is: How can I divide my one sprite sheet into 52 sections and add that to my ArrayList?
This is what I have so far. I know it doesn't work yet, but I'm not entirely sure if I'm on the right track.
//private ImageIcon[][] cards = new ImageIcon[4][13];
private BufferedImage img;
private final int _WIDTH = 74;
private final int _HEIGHT = 94;
public CardGame1(ImageIcon[][] cards){
try{
img = ImageIO.read(getClass().getResource(
"classic-playing-cards.png"));
}catch(Exception e){
e.printStackTrace();
}
for(int r = 0; r < cards.length; r++){
for(int c = 0; c < cards[r].length; c++){
cards[r][c] = new ImageIcon(img.getSubimage(c * _WIDTH,
r * _HEIGHT, _WIDTH, _HEIGHT));
}
}
}
Some one told me to put the ArrayList in another class so here it is:
private JFrame frame;
private JPanel panel;
private Random rand;
private JButton drawCard;
private JLabel card;
private ArrayList<ArrayList<CardGame1>> _cardObj
= new ArrayList<ArrayList<CardGame1>>();
public CardGameGUI(){
gameBoard();
}
public void gameBoard(){
frame = new JFrame("Card Game");
panel = new JPanel();
frame.setSize(600, 500);
frame.setLayout(new GridLayout());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(true);
frame.setVisible(true);
frame.add(panel);
panel.setBackground(Color.GREEN);
drawCard = new JButton("Draw Card!");
drawCard.setSize(100, 50);
panel.add(drawCard);
drawCard.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent arg0) {
}
});
}

These links that should solve your problem
https://docs.oracle.com/javase/8/docs/api/java/awt/image/BufferedImage.html#copyData-java.awt.image.WritableRaster-
http://www.programcreek.com/java-api-examples/index.php?api=java.awt.image.WritableRaster

Need assistance with frogger type game

I'm in the process of creating a frogger type game and have gotten pretty far in getting the program to do what I want it to do. However, I'm starting to think that to finish the game I will have to use way to much code and there must be a simpler way achieve the same results. I'm not looking for an answer, just need some more information.
Question 1: What can I use for the images that represent the moving Icons or cars? I'm currently using JButtons. The problem is that is difficult to get the buttons to move uniformly and I want to use 24 different moving Icons and from what I've learned so far I will have to add a new JButton for each icon.
Question 2: The way that I've gotten the Jbutton icons to move is to use a timer delay and then a counter to increment the x values. This works for the most part, but is there a better, perhaps simpler, way to move icons across the screen?
Any tips, tutorials etc are greatly appreciated.
Here is one of the classes that I've created to get movement of the icons:
public class EnemyJPanel extends JButton {
JButton enem = new JButton();
JButton enem12 = new JButton();
JButton enem13 = new JButton();
JButton enem1 = new JButton("1");
JButton enem2 = new JButton("2");
JButton enem3 = new JButton("3");
JButton enem4 = new JButton("4");
JButton score = new JButton("Score");
JButton enem5 = new JButton("5");
JButton enem6 = new JButton("6");
JButton enem7 = new JButton("7");
JButton enem8 = new JButton("8");
JButton yard = new JButton("50 Yard Line");
int i = 16;
int u = 576;
int d = 16;
int n = 576;
int k = 16;
int l = 16;
int dummyval = 16;
public EnemyJPanel(){
super();
setLayout(null);
enem1.setBounds(16,300,40,55);
enem2.setBounds(16,245,40,55);
enem3.setBounds(16,190,40,55);
enem4.setBounds(16,135,40,55);
score.setBounds(16,80,601,55);
yard.setBounds(16,355,601,55);
enem5.setBounds(16,410,40,55);
enem6.setBounds(16,465,40,55);
enem7.setBounds(16,520,40,55);
enem8.setBounds(16,575,40,55);
enem12.setBounds(16,300,40,55);
enem13.setBounds(16,300,40,55);
add(enem1);
add(enem2);
add(enem3);
add(enem4);
add(score);
}
public void addEnemy(){
enem1.setBounds(16,300,40,55);
enem2.setBounds(16,245,40,55);
enem3.setBounds(16,190,40,55);
enem4.setBounds(16,135,40,55);
score.setBounds(16,80,601,55);
add(enem1);
add(enem2);
add(enem3);
add(enem4);
add(score);
}
public void enemyMovement(){
i++;u--;d++;n--; // increments lateral movement from a timer in
dummyval++; // the dummy value is needed to keep the icons looping
dummyval = dummyval + 2;
enem1.setBounds(i,300,40,55);
i = i + 2;
if (dummyval > 176){
k++; k = k + 2;
enem12.setBounds(k,300,40,55);
}
if (k > 176){
l++;
l = l + 2;
enem13.setBounds(l,300,40,55);
}
enem2.setBounds(u,245,40,55);
enem3.setBounds(d,190,40,55);
enem4.setBounds(n,135,40,55);
enem5.setBounds(i,410,40,55);
enem6.setBounds(u,465,40,55);
enem7.setBounds(d,520,40,55);
enem8.setBounds(n,575,40,55);
if(i > 576){ // resets button
i = 16;
}
if(k > 576){
k = 16;
}
if(u < 16){
u = 576;
}
u = u - 2; // increase lateral speed
if(d == 576) {
d = 16;
}
if(n < 16){
n = 576;
}
n = n - 5; //increases lateral speed
}
}

The problem is created because you try to manage all the "stuff" separately. It looks like you may be missing some basic information on classes
First, I would create a custom class, something like
class ButtonObject extends JButton
{
public ButtonObject(String text, int x, int y, int width, int height)
{
super(text);
this.setBounds(x, y, width, height);
}
}
You also may want to take a look at arrays and create an array of your new ButtonObject.
The for loop will help you get through all the objects in your array.
ButtonObject[] enemies = new ButtonObject[10];
for (int i = 0; i < 10; i++)
{
String text = String.valueOf(i);
int y = 300 - (i * 55);
enemies[i] = new ButtonObject(text, 16, y, 40, 55);
}
There is probably a better way to do it than buttons but you may want to stick with them for now for simplicity.

Java - Filling an array of JLabels with ImageIcons via loop(NullPointerException)

the basic aim is to have a JPanel filled with 9 white squares in a 3x3 pattern; The squares are 150x150 blank white .jpg files. It must be this way since later on, the program will have to change the blank squares to one of a selection of simple images, and must be able to change any square at any time.
The problem, simply, is I'm getting a NullPointerException. I have to assume it's something to do with initialising the array as null but NetBeans(yes, NetBeans...) seems to get angry with me if I don't do that. Same if I try to declare the size of the array. (That would be... "ArrayType[arraysize] arrayName;", yes?"
Egh, I'm just guessing wildly.
Edit - NullPointerException fixed, but now the blank(white) images are simply not appearing in the frame. Code below edited to reflect its new state, more potentially relevant lines added.
Here be all relevant code:
JFrame controller = new JFrame("SmartHome Interface");
controller.setVisible(true);
controller.setSize(480,500);
controller.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
//[...]
JPanel labelPanel = new JPanel();
//[...]
labelPanel.setBackground(Color.GREEN);
//[...]
ImageIcon blank = new ImageIcon("../Images/blank.jpg");
//[...]
controller.add(labelPanel);
//[...]
JLabel[] labels = new JLabel[9];
for (int i = 0; i <= 8; i++)
{
int xLowBound;
int xUpBound;
int yLowBound;
int yUpBound;
//Maths for positioning the labels correctly. Should be 150px in size with 10px gaps each.
xLowBound = (i % 3) * 160;
xUpBound = xLowBound + 150;
yLowBound = (i / 3) * 160;
yUpBound = yLowBound + 150;
labels[i] = new JLabel();
labels[i].setIcon(blank);
labels[i].setBounds(xLowBound, yLowBound, xUpBound, yUpBound);
labelPanel.add(labels[i]);
}
Also.....is the filepath for the ImageIcon correct?
The code itself being located in "src/smarthome" and the images in "src/Images"
And apologies if I broke any forum conventions/codes of conduct/etc. Newby here, tried to be careful not to but I may have forgotten something.

Your problem reduces to this:
JLabel[] labels = null;
for (int i = 0; i <= 8; i++) {
labels[i].setIcon(blank);
}
This code fragment will fail because labels == null. Therefore labels[i] == null.
Use this instead:
JLabel[] labels = new JLabel[9];
for (int i = 0; i <= 8; i++) {
labels[i] = new JLabel();
labels[i].setIcon(blank);
}

Your filepath for imageIcons is incorrect. You should use:
ImageIcon img = new ImageIcon(getClass().getResource("../Images/blank.jpg"));
if your code is in static method use this:
ImageIcon img = new ImageIcon(YourClass.class.getResource("../Images/blank.jpg"));
There is a good answer about loading image icons(thanks to nIcE cOw).
You should call setVisible() and setSize() after adding all components to the frame.
Add components to frame's content pane(frame.getContentPane()).
You always should place your GUI code in separate thread.
So, your code will be:
SwingUtilities.invokeLater(new Runnable()
{
#Override
public void run()
{
JFrame controller = new JFrame("SmartHome Interface");
controller.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel labelPanel = new JPanel();
labelPanel.setBackground(Color.GREEN);
// !!!
ImageIcon blank = new ImageIcon(YourClass.class
.getResource("../Images/blank.jpg"));
// !!!
controller.getContentPane().add(labelPanel);
JLabel[] labels = new JLabel[9];
for (int i = 0; i <= 8; i++)
{
int xLowBound;
int xUpBound;
int yLowBound;
int yUpBound;
xLowBound = (i % 3) * 160;
xUpBound = xLowBound + 150;
yLowBound = (i / 3) * 160;
yUpBound = yLowBound + 150;
labels[i] = new JLabel();
labels[i].setIcon(blank);
labels[i].setBounds(xLowBound, yLowBound, xUpBound,
yUpBound);
labelPanel.add(labels[i]);
}
// !!!
controller.setVisible(true);
controller.setSize(480, 500);
}
});

Custom JButton not sizing properly?

I am creating a matching game using Netbeans, but not the GUI editor (it sucks). So, basically, I created a new class, called Card, that extends the JButton class. Upon construction, the button's size is set to 100px by 100px and an icon is set. When I add the button to a JPanel in a GridBagLayout, it is not the intended size.
Here is some of my code:
JFRAME CLASS:
package matchinggame;
... imports ...
public class MatchingGameWindow extends JFrame {
Card[] cards = new Card[16]; //16 game cards
public MatchingGameWindow() {
...
//Create new game panel (for the cards)
JPanel gamePanel = new JPanel(new GridBagLayout());
//gamePanel.setSize(500,500); removed as it is not needed.
...
this.add(gamePanel, BorderLayout.CENTER);
//Create 16 card objects
cards = createCards();
//Create new grid bag constraints
GridBagConstraints gbc = new GridBagConstraints();
//Add the cards to the game panel
int i=0;
for (int y = 0; y < 4; y++) {
gbc.gridy = y;
for (int x = 0; x < 4; x++) {
gbc.gridx = x;
gamePanel.add(cards[i], gbc);
i++;
}
}
}
public final Card[] createCards() {
Card[] newCards = new Card[16];
//New choices array
ArrayList<Integer> choices = new ArrayList();
int[] choiceValues = {0,0,1,1,2,2,3,3,4,4,5,5,6,6,7,7};
//Add the initial choice values to the arraylist
for (int i=0; i < choiceValues.length; i++) {
choices.add(choiceValues[i]);
}
//Create 16 cards
for (int i=0; i < 16; i++) {
//Initial value of -1 for error checking
int iconIndex = -1;
//Loop until card is created
while (iconIndex == -1) {
//Get a random number from 0 - 7
Random r = new Random();
int rInt = r.nextInt(8);
//If the random number is one of the choices
if (choices.contains(rInt)) {
//the icon # will be the random number
iconIndex = rInt;
//Get rid of that choice (it is used up)
choices.remove(new Integer(rInt));
//Create a new Card in the Card[]
newCards[i] = new Card(i,iconIndex);
//If all the choices are gone
} else if (choices.isEmpty()){
iconIndex = -1; //done creating this card (breaks out of loop)
}
}
}
//Return the created cards
return newCards;
}
}
CARD CLASS:
package matchinggame;
import javax.swing.ImageIcon;
import javax.swing.JButton;
public class Card extends JButton {
final static ImageIcon defaultIcon = new ImageIcon("cardback.jpg");
ImageIcon secretIcon;
boolean isRevealed = false;
...
public Card(final int cardIndex, int secretIconIndex) {
//Size is 100px by 100px
setSize(100, 100);
//Default icon is card back image
setIcon(defaultIcon);
//Get the secret icon behind the back of the card
secretIcon = icons[secretIconIndex];
}
}
And using this code I get a result of this:
Any ideas as to what I am doing wrong here?
EDIT:
I overrided the getPreferredSize method like Hovercraft Full Of Eels said, and it worked!
I added this code in the Card class:
#Override
public Dimension getPreferredSize() {
return new Dimension(100,100);
}
and got my desired result:
Now I must be doing something wrong with the icons, as they are not showing up as they should.

You should not use setSize(...) in the class's constructor but rather override the class's getPreferredSize() method to return a Dimension(100, 100). And in fact you should have setSize(...) no-where in your program. Instead use decent layout managers, call pack() on the JFrame after adding all components and before setting it visible, and let the layout managers size the GUI appropriately.