[vzybilly]

Hopefully someone here can help me quickly, i think the code will say what i want to happen

Current Code Snippet:

	   public Panel03(int size, int sec)
	  {
		 this(size, sec, getC());
	  }
	   public Color[] getC()
	  {
		 Color[] tc = new Color[2];
		 tc[0] = Color.white;
		 tc[1] = Color.black;
		 return tc;
	  }
	   public Panel03(int size, int sec, Color[] c)
	  {

old code:

	   public Panel03(int size, int sec)
	  {
		 this(size, sec, new Color{Color.white, Color.black});
	  }
	   public Panel03(int size, int sec, Color[] c)
	  {

[macosxnerd101]

Can you describe the errors you are getting as well as the context of your code?

[vzybilly]

Sorry, forgot ;

Panel03.java:25: cannot reference this before supertype constructor has been called
		 this(size, sec, getC());
						 ^
1 error

[pbl]

You cannot call an instance method while your object is not created yet and it is not created yet because you invoke another constructor so your object is not created yet and thus getC() is not available yet
However you can make the method static and it will work

public Panel03(int size, int sec)
	  {
		 this(size, sec, getC());
	  }
	   static private Color[] getC()
	  {
		 Color[] tc = new Color[2];
		 tc[0] = Color.white;
		 tc[1] = Color.black;
		 return tc;
	  }
	   public Panel03(int size, int sec, Color[] c)
	  {
	  }
}

[vzybilly]

Yay, it works, thanks~

[macosxnerd101]

In addition to what Pbl said, wouldn't it be easier to make the Color[] an instance variable rather than using a getter each time you want to access it within the class? Then just have a getter method to return a reference to the Color[]. So something like:

public class Panel3{ 
   //as it is an instance variable, the entire class save for static elements can access it
	private Color[] c;

   //this will be your final constructor in your constructor chain
	public Panel3(..params..){
		c = {Color.black, Color.white};
		..other code..
	 }

	 //return a reference to your Color[]
	 public Color[] getC(){return c;}
}

[g00se]

Since that method is effectively immutable, you might as well declare

private final static Color[] INITIAL_COLORS = { Color.white, Color.black };

and use the variable

Quote

wouldn't it be easier to make the Color[] an instance variable rather than using a getter each time you want to access it within the class?

Making it an instance variable wouldn't of course alter the issue, since it's still in a 'pre-instance' context. Making it a class variable does alter the situation, and making it final underlines the essential immutability of the array

This post has been edited by g00se: 21 January 2010 - 03:46 PM

[macosxnerd101]

g00se, on 21 Jan, 2010 - 06:45 PM, said:

Making it an instance variable wouldn't of course alter the issue, since it's still in a 'pre-instance' context. Making it a class variable does alter the situation, and making it final underlines the essential immutability of the array

Agreed. My point was though that he wouldn't have to include it as a param within his constructors.

[pbl]

g00se, on 21 Jan, 2010 - 02:45 PM, said:

Since that method is effectively immutable, you might as well declare

private final static Color[] INITIAL_COLORS = { Color.white, Color.black };

and use the variable

Quote

wouldn't it be easier to make the Color[] an instance variable rather than using a getter each time you want to access it within the class?

Making it an instance variable wouldn't of course alter the issue, since it's still in a 'pre-instance' context. Making it a class variable does alter the situation, and making it final underlines the essential immutability of the array

Agree 100%
Would have done it that way but I wanted to approach the actual problem of invoking an instance method before the object is created

[vzybilly]

i needed the colors in the constructor because i want to be able to call it with other colors, like:

		 Color[] c = new Color[4];
		 c[0] = Color.blue;
		 c[1] = Color.red;
		 c[2] = Color.green;
		 c[3] = Color.yellow;
		 frame.setContentPane(new Panel03(5, 10, c));

[pbl]

vzybilly, on 21 Jan, 2010 - 04:17 PM, said:

i needed the colors in the constructor because i want to be able to call it with other colors, like:

		 Color[] c = new Color[4];
		 c[0] = Color.blue;
		 c[1] = Color.red;
		 c[2] = Color.green;
		 c[3] = Color.yellow;
		 frame.setContentPane(new Panel03(5, 10, c));

does not make sense
how would you change

	 static private Color[] getC()
	  {
		 Color[] tc = new Color[2];
		 tc[0] = Color.white;
		 tc[1] = Color.black;
		 return tc;
	  }

from one call to another ?

[g00se]

Quote

i needed the colors in the constructor because i want to be able to call it with other colors, like:

In that case, you need something like the following:

import java.awt.*;

public class Panel03 {

	private final static Color[] INITIAL_COLORS = { Color.white, Color.black };

	private Color[] colors;
	private int size;
	private int sec; // NOT a good variable name

	public Panel03(int size, int sec) {
	this.size = size;
	this.sec = sec;
	this.colors = INITIAL_COLORS;
	}

	public Panel03(int size, int sec, Color[] c) {
	this(size, sec);
	this.colors = colors;
	}

}

This post has been edited by g00se: 22 January 2010 - 04:50 AM

[vzybilly]

pbl, on 21 Jan, 2010 - 10:35 PM, said:

vzybilly, on 21 Jan, 2010 - 04:17 PM, said:

i needed the colors in the constructor because i want to be able to call it with other colors, like:

		 Color[] c = new Color[4];
		 c[0] = Color.blue;
		 c[1] = Color.red;
		 c[2] = Color.green;
		 c[3] = Color.yellow;
		 frame.setContentPane(new Panel03(5, 10, c));

does not make sense
how would you change

	 static private Color[] getC()
	  {
		 Color[] tc = new Color[2];
		 tc[0] = Color.white;
		 tc[1] = Color.black;
		 return tc;
	  }

from one call to another ?

getC() is used in the constructors with 0,1,2 args. getC() is being used for the 3rd arg in the 3 arg constructor where everything happens. if i called panel like Panel03(5, 10) then getC() will happen, but i call Panle03(5, 10, c) and getC() will not happen. getC() does not change.

This post has been edited by vzybilly: 22 January 2010 - 11:32 AM

[g00se]

Quote

getC() is used in the constructors with 0,1,2 args.

We know what you're attempting to do. It can't be done - for the reasons given above.
See my example for how you can produce the required functionality

[vzybilly]

g00se, on 22 Jan, 2010 - 10:40 AM, said:

Quote

getC() is used in the constructors with 0,1,2 args.

We know what you're attempting to do. It can't be done - for the reasons given above.
See my example for how you can produce the required functionality

If it can't be done, how is it working for me right now?