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Thread: Arraylist help

  1. #1
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    Default Arraylist help

    I'm kind of new at programming, and I'm trying to create an arraylist to hold 6 or 7 colors that can be used in a for loop so that they can be assigned like color(0), color(1), so that in my loop, I can make it say setColor(color(loop)). Loop is my int from my for loop. Basically, each time it runs the loop, I want the color to be the next one in the arraylist.

    for (int loop = 0; loop <= 5; loop++){
        		myPen.setColor(color(loop));
        	}

    Is this possible?


  2. #2
    Administrator copeg's Avatar
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    Default Re: Arraylist help

    ArrayList colors = new ArrayList();
    //add all colors to the list
    for ( int i = 0; i < colors.size(); i++ ){
        myPen.setColor(colors.get(i));
    }

  3. #3
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    Default Re: Arraylist help

    Well, I've been trying since you've posted that, and haven't been able to make it work. I'm not sure if I added the colors to the arraylist correctly, and "myPen.setColor(colors.get(i));" doesn't seem to want to work.

  4. #4
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    Default Re: Arraylist help

    Please post the code and errors you are receiving, both of which are a wealth of information to help solve your problem

  5. #5
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    Default Re: Arraylist help

    Basically it makes a circle centered in a hexagon, but once I figure out how to do this arraylist, I woulld like to make the sides keep changing colors in a pattern for a little bit. I can figure that part out, I just need to figure this out.

    import gpdraw.*;
    import java.awt.Color;
    	import java.util.ArrayList;
     
    public class Benzene {
    	private DrawingTool myPen;
        private SketchPad myPap;
     
        public Benzene(){
        	myPap = new SketchPad(800,800);
        	myPen = new DrawingTool(myPap);
        }
     
        public void draw(){
        	Color cBlue = new Color(0,0,255);
        	Color cRed = new Color(255,0,0);
        	Color cGreen = new Color(0,255,0);
        	Color cPurple = new Color(255,0,255);
        	Color cCyan = new Color(0,255,255);
        	Color cYellow = new Color(255,255,0);
        	Color cOrange = new Color(255,132,0);
        	myPen.setColor(cOrange);
        	myPen.setWidth(4);
        	myPen.drawCircle(100);
        	myPen.up();
        	myPen.move(-70,120);
        	myPen.down();
        	myPen.move(70,120);
     
    		ArrayList colors = new ArrayList();
    		colors.add(cBlue);
    		colors.add(cRed);
    		colors.add(cGreen);
    		colors.add(cPurple);
    		colors.add(cCyan);
    		colors.add(cYellow);
    		colors.add(cOrange);
     
        	for (int i = 0; i <= colors.size(); i++){
        		myPen.setColor(colors.get(i));
    			myPen.turnRight(60);
        		myPen.forward(140);
        	}
     
     
        }
    }

    setColor(java.awt.Color) in gpdraw.DrawingTool cannot be applied to (java.lang.Object)




    I have a feeling that I added the colors incorrectly.

  6. #6
    Administrator copeg's Avatar
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    Default Re: Arraylist help

    ArrayList is generic, so if you do not define the objects put in, you must do so when you take them out. Solution 1 is to cast the object when you get it from the list
    myPen.setColor((Color)colors.get(i));
    Solution 2 - which provides compile time checks - is to use generics
    ArrayList<Color> colors = new ArrayList<Color>();

  7. The Following User Says Thank You to copeg For This Useful Post:

    TreeChopper (September 16th, 2010)

  8. #7
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    Default Re: Arraylist help

    Hi TreeChopper,

    you need to replace

    for (int i = 0; i <= colors.size(); i++){
    myPen.setColor(colors.get(i));
    with

    for (int i = 0; i <= colors.size(); i++){
    myPen.setColor((Color)(colors.get(i)));
    because get() method will return Object class object which we need to cast explicitly to get our required object.

  9. The Following User Says Thank You to ramanjaneyulu For This Useful Post:

    TreeChopper (September 16th, 2010)

  10. #8
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    Default Re: Arraylist help

    Thank you very much, it works exactly how I wanted it to.

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