Question

When I invoke the forward or backward method the current_number isnt being changed. Not sure if its something in my switch case or my methods..

package project4;

import java.awt.image.BufferedImage;
import java.net.URL;
import java.util.Scanner;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class PictureViewer {

final static int MIN_NUMBER = 0;
final static int MAX_NUMBER = 8;
static int image_number = 1;
  

public static int forward(int current_number) {
if (current_number < MAX_NUMBER) {
return current_number ++;
} else if (current_number > MAX_NUMBER) {
return MIN_NUMBER;
}
return current_number;
}

public static int backward(int current_number) {
if (current_number > MIN_NUMBER) {
return current_number--;
} else if (current_number <= MIN_NUMBER) {
return MIN_NUMBER;
}
return current_number;
}

public static String createFileName(int current_number) {
String imageString = "picture" + current_number + ".jpg";
return imageString;
}

public static String createRandomName() {
int random_number = 1 + (int) (Math.random() * (MAX_NUMBER - MIN_NUMBER) + 1);
String imageString = "picture" + random_number + ".jpg";
return imageString;
}

public static void showMenu() {
Scanner input = new Scanner(System.in);
while (true) {
System.out.println("Select One of the Options");
System.out.println("Option 1: Forward");
System.out.println("Option 2: Backward");
System.out.println("Option 3: Create File Name");
System.out.println("Option 4: Create Random Name");

int current_number = 0;
int user = input.nextInt();

switch (user) {
case 1:
System.out.println("static forward");
forward(current_number);   
  
break;
case 2:
System.out.println("static backward");
backward(current_number);

break;
case 3:
System.out.println("createFileName");
showWindow(createFileName(current_number));
break;
case 4:
System.out.println("createRandomName");
showWindow(createRandomName());
break;

}
}
}
public void forward() {

if (image_number < MAX_NUMBER) {
image_number++;
} else {
image_number = MAX_NUMBER;
}
}

public void backward() {

if (image_number > MIN_NUMBER) {
image_number--;
}
}

public static void main(String[] args) {

showMenu();
}

public static void showWindow(String filename) {
JPanel myPanel = new JPanel();
JFrame pictureFrame = new JFrame();
pictureFrame.setTitle(filename);
pictureFrame.setSize(800, 600);
pictureFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
myPanel.add(load_picture(filename));
pictureFrame.add(myPanel);
pictureFrame.setVisible(true);
}

public static JLabel load_picture(String imagefile) {
JLabel templabel = null;
String startURL = "";
if (!imagefile.startsWith("http")) {
startURL = "http://riveira.x10host.com/CMPSCI111L/images/";
}
URL myURL = null;
try {
myURL = new URL(startURL + imagefile);
BufferedImage myPicture = ImageIO.read(myURL);
templabel = new JLabel(new ImageIcon(myPicture));
} catch (Exception e) {
System.out.println("Error caught " + e.toString());
}
return templabel;
}
}

Answer 1

The problem with your code is that though you are calling the forward and backward methods , you are not saving the state of current number after the function call. To tell you in simple terms, store the return value of those functions.

So, replace your function calls as below.

case 1:
System.out.println("static forward");
current_number = forward(current_number);   
  
break;
case 2:
System.out.println("static backward");
current_number = backward(current_number);

break;