display an error msg saying wrong format.

[safra]

hi everybody..
i need help with my assignment.i want to display a error message saying that the user has inputed a string where an integer is needed.because when i enter "h" (for an example) in the x coordinate field the system crashes.i want to display an error message instead.

/**
 * A program that simulates an ant taking a step on a sheet of paper. stage 2
 * 
 * @author (safra)
 * @version (18/8/2010)
 */
import java.util.Scanner;
import javax.swing.JOptionPane;
public class Stage2a
{
    public static void main(String[] args)
    {
        final int WIDTH = 100; // width of the sheet in pixels
        final int HEIGHT = 100; // height of the sheet in pixels
        
        String input;
        String input1;
        int x; // the x-coordinate
        int y; // the y-coordinate
        int steps;// the number of steps to be taken
      
      
       input = JOptionPane.showInputDialog ("Enter your ant's x-coordinate: ");
       x = Integer.parseInt (input);
       
       if(x < 0 || x > WIDTH-1) //checking if it's in the range
        {
            JOptionPane.showMessageDialog (null,"The x-coordinate must be between 0 and " + (WIDTH-1));
            System.exit(-1);
            
        }
       input = JOptionPane.showInputDialog("Enter your ant's y coordinate: ");
       y = Integer.parseInt(input);
       
       if (y <0 || y > HEIGHT-1)
       {
           JOptionPane.showMessageDialog (null,"The y-coordinate must be between 0 and " + (HEIGHT-1));
           System.exit(-1);
          
        }
        
      	input = JOptionPane.showInputDialog ("Enter your ant's direction");
      	
        
      //the number of steps
        input1 = JOptionPane.showInputDialog ("How many steps should the ant take?");
        steps = Integer.parseInt(input1);

       for (int z=1;z<=steps;z++)
       {
     
       
       if(input.equalsIgnoreCase("U"))//increasing or decresing the coordinates according to direction
        {
            y =++y;
        }
       else if (input.equalsIgnoreCase("UR")) 
        {
            y =++y;
            x =++x;
        }
        else if (input.equalsIgnoreCase("UL"))
        {   
            y =++y;
            x =--x;
        }
        else if (input.equalsIgnoreCase("R"))
        {
            x = ++x;
        }
        else if (input.equalsIgnoreCase("DR"))
        {
            y =--y;
            x =++x;
        }

        else if (input.equalsIgnoreCase("D"))
        {
            y =--y;
        }
        else if (input.equalsIgnoreCase("DL"))
        {
            y =--y;
            x =--x;
        }
        else if (input.equalsIgnoreCase("L"))
        {
            x =--x;
        }
        else 
        {JOptionPane.showMessageDialog (null,"Please enter one of the following: \n U,UR,UL,D,DR,DL,L,R");
        System.exit (-1);}
        }

        // "Wrap" the x and y-coordinates if the ant has walked over the edge of the paper
        if(x < 0)
        {
            x += WIDTH;
        }
        else if (x > WIDTH-1)
        {
            x=x-WIDTH;
        }
        
        if (y < 0)
        {
            y += HEIGHT;
        }
         else if (y > HEIGHT-1)
        {
            y=y-HEIGHT;
        }
       
        
       JOptionPane.showMessageDialog (null,"The new x coordinate is: " + x + "\n the new y coordinate is: " + y);
        
    }
}

[Dheeraj Joshi]

wrap your code in try catch for handling the exceptional cases.

Regards
Dheeraj Joshi

[safra]

umm..i dont exactly know how to do that.i have very little knowledge in java..im still new to this field. do you think you can teach me how its done? please..

[ahmee]

Check this out.I used TRY CATCH statement.

import java.util.Scanner;
import javax.swing.JOptionPane;
class Stage2a
{
public static void main(String[] args)
{
String D_Play="the user has inputed a string where an integer is needed";
	try{

final int WIDTH = 100; // width of the sheet in pixels
final int HEIGHT = 100; // height of the sheet in pixels

String input;
String input1;
int x; // the x-coordinate
int y; // the y-coordinate
int steps;// the number of steps to be taken


input = JOptionPane.showInputDialog ("Enter your ant's x-coordinate: ");
x = Integer.parseInt (input);

if(x < 0 || x > WIDTH-1) //checking if it's in the range
{
JOptionPane.showMessageDialog (null,"The x-coordinate must be between 0 and " + (WIDTH-1));
System.exit(-1);

}
input = JOptionPane.showInputDialog("Enter your ant's y coordinate: ");
y = Integer.parseInt(input);

if (y <0 || y > HEIGHT-1)
{
JOptionPane.showMessageDialog (null,"The y-coordinate must be between 0 and " + (HEIGHT-1));
System.exit(-1);

}

input = JOptionPane.showInputDialog ("Enter your ant's direction");


//the number of steps
input1 = JOptionPane.showInputDialog ("How many steps should the ant take?");
steps = Integer.parseInt(input1);

for (int z=1;z<=steps;z++)
{


if(input.equalsIgnoreCase("U"))//increasing or decresing the coordinates according to direction
{
y =++y;
}
else if (input.equalsIgnoreCase("UR"))
{
y =++y;
x =++x;
}
else if (input.equalsIgnoreCase("UL"))
{
y =++y;
x =--x;
}
else if (input.equalsIgnoreCase("R"))
{
x = ++x;
}
else if (input.equalsIgnoreCase("DR"))
{
y =--y;
x =++x;
}

else if (input.equalsIgnoreCase("D"))
{
y =--y;
}
else if (input.equalsIgnoreCase("DL"))
{
y =--y;
x =--x;
}
else if (input.equalsIgnoreCase("L"))
{
x =--x;
}
else
{JOptionPane.showMessageDialog (null,"Please enter one of the following: \n U,UR,UL,D,DR,DL,L,R");
System.exit (-1);}
}

// "Wrap" the x and y-coordinates if the ant has walked over the edge of the paper
if(x < 0)
{
x += WIDTH;
}
else if (x > WIDTH-1)
{
x=x-WIDTH;
}

if (y < 0)
{
y += HEIGHT;
}
else if (y > HEIGHT-1)
{
y=y-HEIGHT;
}


JOptionPane.showMessageDialog (null,"The new x coordinate is: " + x + "\n the new y coordinate is: " + y);
	}

	catch(Exception e){
JOptionPane.showMessageDialog (null,D_Play," Alert", JOptionPane.ERROR_MESSAGE);
}
}
}

[ahmee]

This is an simple try catch statement program check it out it will help you to understand try catch better

import javax.swing.*;

   class demo
{
       public static void main(String[] args){
  String Dplay= "you have not enter an integer";
       try
{
       String  enter=JOptionPane.showInputDialog("enter num");
       int  i=Integer.parseInt(enter);

       if(i==1){
       JOptionPane.showMessageDialog(null,"you hit the rite number");

}}
/////else if you enter any/////char then catch statement/////will excutes
		catch(Exception e)
{
		JOptionPane.showMessageDialog(null,Dplay,"Alert",JOptionPane.ERROR_MESSAGE);

}

}
}

[safra]

wow..!!! worked perfectly..!! owe you big time!!! thanks alooootttt!!!! yay!! happiness in da air!! hehehe

[ahmee]

you welcome...