矩阵的杜利特尔分解

public class Main {
    double a[][] = new double[][]{{2, 1, 5}, {4, 1, 12}, {-2, -4, 5}};
    public static void main(String[] args) {
        new Main();
    }
    Main() {
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[0].length; j++) {
                for (int k = 0; k < Math.min(i, j); k++) {
                    a[i][j] -= a[i][k] * a[k][j];
                }
                if (i > j)
                    a[i][j] /= a[j][j];
            }
        }
        for (int i = 0; i < a.length; i++) {
            for (int j = 0; j < a[0].length; j++) {
                System.out.print(" " + a[i][j]);
            }
            System.out.println();
        }
    }
}