/** SquareMatrix: * quadratic matrix of doubles */ public class SquareMatrix extends Matrix { /** creates an n x n square matrix */ public SquareMatrix(int n) { super(n,n); } /** matrix multiplication of square matrices gives a square matrix */ public void mult(SquareMatrix b, SquareMatrix result) { super.mult(b, result); } /** returns the trace of a square matrix */ public double trace() { double tr = 0.0; for (int i = 0; i < nRows; i++) { tr += val[i + nRows * i]; } return tr; } }