Java Generics and numbers

Question

In an attempt to see if I can clean up some of my math code, mostly matrix stuff, I am trying to use some Java Generics. I have the following method:

private <         


        

Answer 1

it should be null instead of zero.

If you want to actually put in there the equivalent 0 for object T you will need to provide a factory of T. Something like this:

interface Factory {
   T getZero();     
}

and you should make the method like this:

private  T[][] zeroMatrix(int row, int col, Factory factory) {
    T[][] retVal = (T[][])new Object[row][col];
    for(int i = row; i < row; i++) {
        for(int j = col; j < col; j++) {
            retVal[i][j] = factory.getZero();
        }
    }

    return retVal;
}

You should also have proper implementations for the factory:

 class IntegerFactory implements Factory {
    Integer getZero() {
       return new Integer(0);
    }
}

Normally you would put the getMatrix(int row, int column) in the factory implementation too in order to actually return a proper typed array.