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Thread: If-Else Statement help

  1. #1
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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..

    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; February 9th, 2010 at 08:06 AM. Reason: Please use code tags


  2. #2
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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.

  3. #3
    Super Moderator Json's Avatar
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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

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

    // Json

  4. #4
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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.

  5. #5
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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?

    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);}
     
     
        			}
     
     
     
     
     
        	{
    }
        		}

  6. #6
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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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