Thread: About loop

I'm not sure what you are trying to do but

 matrix[x][y]

is a location in your two-dimensional int array, so you need to assign it an int value. For example

matrix[x][y] = 13;

I want to set matrix[0][0]=5, matrix[0][1]=5 ... matrix[200][200] = 5
I want to use for loop to do so but it needs to work in a method.
Outside a method, I can't use for loop so i need to write a lot for my purpose.

Can you explain the problem you are facing now? You have the "setMartixZero()" method which set all the matrix[][] locations equal to 5. You can just call it when you want.

If you are facing error/exception, paste here the full text so that we could have a look.
Also, i can assume there must be index out of bound exception. Coz, you are trying to save the value 5 at matrix[200][200] as the total size of your array is 200X200 which means matrix[199][199] will be the last row and column of your array.

I made a careless mistake here.
My code is fine now but I want to ask how i can set matrix[0][0]=5, matrix[0][1]=5 ... matrix[200][200] = 5
by using loop? A loop can only be performed inside a method.

A loop can only be performed inside a method.

Can you provide me with the reference material where you've studied that a loop can not perform inside a method???? Loop can be placed anywhere in your code. Place it in main() and don't make a separate method for initializing the array(if only you intended to do this).

how i can set matrix[0][0]=5, matrix[0][1]=5 ... matrix[200][200] = 5

If you want to use matrix[200][200], don't forget to change the size of array to matrix[201][201] or face the exception.

Originally Posted by Mr.777

Can you provide me with the reference material where you've studied that a loop can not perform inside a method???? Loop can be placed anywhere in your code. Place it in main() and don't make a separate method for initializing the array(if only you intended to do this).

If you want to use matrix[200][200], don't forget to change the size of array to matrix[201][201] or face the exception.

Sorry, are there any misunderstanding? I mean that loop can only be placed inside a method. Outside a method, there is an error. So what i should do if I want to declare
matrix[0][0] = 5, matrix[0][1] = 5, ... , matrix[200][200] = 5.

Class Matrix{
        int x,y;
        int[][] matrix = new int[201][201];
        for(x=1 ; x<=200; x++) //there will be an error because of outside the method
            for(y=1; y<=200; y++)
                matrix[x][y] = 5; 
}

Thank you.

Originally Posted by andreas90

Can you explain the problem you are facing now? You have the "setMartixZero()" method which set all the matrix[][] locations equal to 5. You can just call it when you want.

Do you mean that I can only set all the matrix[][] locations equal to 5 with a method?
Because I want to do the following thing but it seems so stupid.

 static int[][] matrix = {{5 /* x200 times */ }};

Thank you.

You can never write loops inside the class like this. You need to have a main() method to start your program. In the main(), use the loop and do whatever you want to do. Like;

class A{
   public int x;
   public static void main(String[] args){
   x = 5;
   }
}

Originally Posted by Mr.777

You can never write loops inside the class like this. You need to have a main() method to start your program. In the main(), use the loop and do whatever you want to do. Like;

class A{
   public int x;
   public static void main(String[] args){
   x = 5;
   }
}

But I need to initiallise matrix[0][0]=5, matrix[0][1]=5 ... matrix[200][200] = 5 in a class which does not have main class. May i know that if there are any ways i can do it other than using a method.Thank you

Originally Posted by tommyabc

Do you mean that I can only set all the matrix[][] locations equal to 5 with a method?
Because I want to do the following thing but it seems so stupid.

 static int[][] matrix = {{5 /* x200 times */ }};

Thank you.

The for loops are setting ALL the indexes of your int array equal to 5. This what you want to do as far as i understand.

Originally Posted by tommyabc

But I need to initiallise matrix[0][0]=5, matrix[0][1]=5 ... matrix[200][200] = 5 in a class which does not have main class. May i know that if there are any ways i can do it other than using a method.Thank you

You can put the for loops in a separate method which you can call when you want to initialise "matrix[][]".
And as Mr.777 and snowguy13 have mentioned be careful with your array indexes (200 indexes are from 0 to 199).

Originally Posted by snowguy13

No, you need to use a method. But it isn't that complicated. When you typed this code:

        for(x=1 ; x<=200; x++)
            for(y=1; y<=200; y++)
                matrix[x][y] = 5;

it was very close to perfect. The one thing you must remember is that arrays start at index 0 (not at index 1).

Then i will use a method to do it. Thank you.

Or you can use a constructor instead.