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  #1 (permalink)  
Old 08-02-2010, 05:40 PM
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Default If-Else Statement help
Hello,

I just recently started a Java programming class and the current assignment is to create a program that asks the user if they are happy. Depending on the response either a smiley face or sad face appears in a window.

I have been struggling to figure out how to set up an if-else statement, and am also unsure of when to use:
public static void main(String[] args)

I know this is probably very basic level stuff but I've tried messing around with the code for over 2 hours now. This is how far I've gotten..

Java Code
import java.awt.Graphics;
import java.util.Scanner;

import javax.swing.JApplet;

/**
 *This is a program that displays different faces
 *based off of different responses.  
 *2/5/2010
 */
public class Program3
extends JApplet {
    public static final int FACE_DIAMETER = 200;
    public static final int X_FACE = 100;
    public static final int Y_FACE = 50;
    public static final int EYE_WIDTH = 10;
    public static final int EYE_HEIGHT = 20;
    public static final int X_RIGHT_EYE = 155;
    public static final int Y_RIGHT_EYE = 100;
    public static final int X_LEFT_EYE = 200;
    public static final int Y_LEFT_EYE = Y_RIGHT_EYE;
    public static final int MOUTH_WIDTH = 100;
    public static final int MOUTH_HEIGHT = 200;
    public static final int X_MOUTH = 150;
    public static final int Y_MOUTH = 160;
    public static final int MOUTH_START_ANGLE = 180;
    public static final int MOUTH_EXTENT_ANGLE = 180;
    
    public void init()
    {
        setSize(500, 500);
    }
    
    
    public void happyFace (Graphics canvas)
    {
        //Draw face outline
        canvas.drawOval (X_FACE, Y_FACE, FACE_DIAMETER, FACE_DIAMETER);
        
        //Draw eyes
        canvas.fillOval (X_RIGHT_EYE, Y_RIGHT_EYE, EYE_WIDTH, EYE_HEIGHT);
        canvas.fillOval (X_LEFT_EYE, Y_LEFT_EYE, EYE_WIDTH, EYE_HEIGHT);
        
        //Draw mouth
        canvas.drawArc (X_MOUTH, Y_MOUTH, MOUTH_WIDTH, MOUTH_HEIGHT,
                MOUTH_START_ANGLE, MOUTH_EXTENT_ANGLE);
    }
    
    public void sadFace (Graphics canvas)
    {
    }
    	private static final long serialVersionUID = 1L;
    	public static final int FACE_DIAMETER2 = 200;
    	public static final int X_FACE2 = 100;
    	public static final int Y_FACE2 = 50;
    	
    	public static final int EYE_WIDTH2 = 10;
    	public static final int EYE_HEIGHT2 = 20;
    	public static final int X_RIGHT_EYE2 = 155;
    	public static final int Y_RIGHT_EYE2 = 100;
    	public static final int X_LEFT_EYE2 = 200;
    	public static final int Y_LEFT_EYE2 = Y_RIGHT_EYE;
    	
    	public static final int MOUTH_WIDTH2 = 100;
    	public static final int MOUTH_HEIGHT2 = 200;
    	public static final int X_MOUTH2 = 150;
    	public static final int Y_MOUTH2 = 150;
    	public static final int MOUTH_START_ANGLE2 = 150;
    	public static final int MOUTH_EXTENT_ANGLE2 = -120;
  
    	public void paint(Graphics canvas)
    	{
    		//Draw face outline:
    		canvas.drawOval(X_FACE2, Y_FACE2, FACE_DIAMETER2, FACE_DIAMETER2);
    		//Draw eyes:
    		canvas.fillOval(X_RIGHT_EYE2, Y_RIGHT_EYE2, EYE_WIDTH2, EYE_HEIGHT2);
    		canvas.fillOval(X_LEFT_EYE2, Y_LEFT_EYE2, EYE_WIDTH2, EYE_HEIGHT2);
    		//Draw mouth:
    		canvas.drawArc(X_MOUTH2, Y_MOUTH2, MOUTH_WIDTH2, MOUTH_HEIGHT2,
    				MOUTH_START_ANGLE2, MOUTH_EXTENT_ANGLE2);
    
    	happyFace (canvas);
    	sadFace (canvas);
    	
    	
    //The following code deals with if-else and asking the user if they are happy
    	
    	System.out.println("Are you happy?");
    	
    	if (answer == 'y') || (answer == 'yes')
    	
    		
    	}
     
    	{
}

}
Thanks for any advice!



Last edited by Json; 09-02-2010 at 01:06 PM. Reason: Please use code tags
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  #2 (permalink)  
Old 09-02-2010, 02:50 AM
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Default Re: If-Else Statement help
Hi,

i will try to help you out a bit

The method "public static void main(String[] args)" is basically only needed as entry point for standard java programs, if your applet is run from a browser you wont need that function.

And about the if,i would better write it in a way like

if ((answer.equalsIgnoreCase("y") || (answer.equalsIgnoreCase("yes")) {
....

this ensures String comparison is used, and if the user types Y or YES it will be also valid.
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Old 09-02-2010, 01:08 PM
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Default Re: If-Else Statement help
And to use best practises with this you want to turn it around as well

Java Code
if (("y".equalsIgnoreCase(answer) || ("yes".equalsIgnoreCase(answer)) {
// Json
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Old 09-02-2010, 08:30 PM
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Default Re: If-Else Statement help
I tried your suggestions but it says answer cannot be resolved--what does that mean? Also, I'm running this program from eclipse.
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Old 09-02-2010, 10:11 PM
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Default Re: If-Else Statement help
Okay everything is working as far as I can tell, BUT...when the program loads it won't allow me to add input using the keyboard. Is it the braces? Or is there some coding wrong?

Java Code
import java.awt.Graphics;
import java.util.Scanner;

import javax.swing.JApplet;

/**
 *This is a program that displays different faces
 *based off of different responses.  
 *2/5/2010
 */
public class Program3 extends JApplet
{
public static void main(String[] args)
{System.out.println("Are you happy?");


}	public static final int FACE_DIAMETER = 200;
    public static final int X_FACE = 100;
    public static final int Y_FACE = 50;
    public static final int EYE_WIDTH = 10;
    public static final int EYE_HEIGHT = 20;
    public static final int X_RIGHT_EYE = 155;
    public static final int Y_RIGHT_EYE = 100;
    public static final int X_LEFT_EYE = 200;
    public static final int Y_LEFT_EYE = Y_RIGHT_EYE;
    public static final int MOUTH_WIDTH = 100;
    public static final int MOUTH_HEIGHT = 200;
    public static final int X_MOUTH = 150;
    public static final int Y_MOUTH = 160;
    public static final int MOUTH_START_ANGLE = 180;
    public static final int MOUTH_EXTENT_ANGLE = 180;
  
    
      
    public void happyFace (Graphics canvas)
    {happyFace (canvas);
        //Draw face outline
        canvas.drawOval (X_FACE, Y_FACE, FACE_DIAMETER, FACE_DIAMETER);
        
        //Draw eyes
        canvas.fillOval (X_RIGHT_EYE, Y_RIGHT_EYE, EYE_WIDTH, EYE_HEIGHT);
        canvas.fillOval (X_LEFT_EYE, Y_LEFT_EYE, EYE_WIDTH, EYE_HEIGHT);
        
        //Draw mouth
        canvas.drawArc (X_MOUTH, Y_MOUTH, MOUTH_WIDTH, MOUTH_HEIGHT,
                MOUTH_START_ANGLE, MOUTH_EXTENT_ANGLE);
    }
    
    public void sadFace (Graphics canvas)
    {sadFace (canvas);}
    	private static final long serialVersionUID = 1L;
    	public static final int FACE_DIAMETER2 = 200;
    	public static final int X_FACE2 = 100;
    	public static final int Y_FACE2 = 50;
    	
    	public static final int EYE_WIDTH2 = 10;
    	public static final int EYE_HEIGHT2 = 20;
    	public static final int X_RIGHT_EYE2 = 155;
    	public static final int Y_RIGHT_EYE2 = 100;
    	public static final int X_LEFT_EYE2 = 200;
    	public static final int Y_LEFT_EYE2 = Y_RIGHT_EYE;
    	
    	public static final int MOUTH_WIDTH2 = 100;
    	public static final int MOUTH_HEIGHT2 = 200;
    	public static final int X_MOUTH2 = 150;
    	public static final int Y_MOUTH2 = 150;
    	public static final int MOUTH_START_ANGLE2 = 150;
    	public static final int MOUTH_EXTENT_ANGLE2 = -120;
  
    	@SuppressWarnings({ "unused", "null" })
		public void paint(Graphics canvas)
    	{
    		//Draw face outline:
    		canvas.drawOval(X_FACE2, Y_FACE2, FACE_DIAMETER2, FACE_DIAMETER2);
    		//Draw eyes:
    		canvas.fillOval(X_RIGHT_EYE2, Y_RIGHT_EYE2, EYE_WIDTH2, EYE_HEIGHT2);
    		canvas.fillOval(X_LEFT_EYE2, Y_LEFT_EYE2, EYE_WIDTH2, EYE_HEIGHT2);
    		//Draw mouth:
    		canvas.drawArc(X_MOUTH2, Y_MOUTH2, MOUTH_WIDTH2, MOUTH_HEIGHT2,
    				MOUTH_START_ANGLE2, MOUTH_EXTENT_ANGLE2);
    
    		{ 
    Object answer;
	{Scanner keyboard = new Scanner(System.in);
    answer = keyboard.nextLine();}
    
    			
    			
    			
    			
				if ((answer.equals("y") || (answer.equals("yes")))) Statement:   {
    				happyFace (canvas);
    			}
    			else sadFace (canvas);}
    				
    				
    			}
	 		
			
			      		

         
    	{
}
    		}
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Old 10-02-2010, 12:57 AM
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Default Re: If-Else Statement help
Well i guess it is cause you can't use "System.in" for applets

I have found this link explaining how to get key input in applets:
Applet Tutorial: Keyboard Input

I hope you can use it for JApplet too
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