code: public static ImmutableMatrix zeros(final int rows, final int cols) {
  		if (rows <= 0 || cols <= 0) throw new IllegalArgumentException("Invalid dimensions");
  		return create(new ImmutableData(rows, cols) {
  			@Override
  			public double getQuick(int row, int col) {
  				return 0;
  			}
  		});
  	}
docs: Returns an immutable matrix of the specified size whose elements are all 0.
  
  @param rows the number of rows
  @param cols the number of columns
  @return a <code>rows</code>×<code>cols</code> matrix whose elements are all 0
  @throws IllegalArgumentException if either argument is non-positive