ArrayList Multiplication - HELP!!!

HelloWorld · #1 (**permalink**) 08-01-2007, 07:31 PM

I want to do something like this:

PHP Code:

  ((ArrayList)res.get(i)).add(+= (ArrayList)matrix1.get(i)).get(j) * ((ArrayList)matrix2.get(j)).get(i));

Is there anyway I can do that

ccoonen · #2 (**permalink**) 08-14-2007, 10:16 PM

So when you break it down you want to do multiplication elements from already existing elements?

res.get(i) += matrix1.get(i).get(j) * matrix2.get(j).get(i);

Not positive in Java but maybe res[i] += matrix1[i][j] * matrix2[j][i];

Is that the gyst of your equation?

HelloWorld · #3 (**permalink**) 08-14-2007, 10:59 PM

LOL, thanx ccoonen

Quote:

Not positive in Java but maybe res[i] += matrix1[i][j] * matrix2[j][i];

that's exactly the problem is, I know on how to do it in the multi dimensional arrays, but I wanted to do it in the ArrayList

Moreover, I want to keep it formed as a Matrix, not a single ArrayList as the first example that you gave me...

Code:


res.get(i) += matrix1.get(i).get(j) * matrix2.get(j).get(i);

can't do this because res.get(i) is an object, *you can only use += to the primitive type of variables

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