class Mat2f {
    private final float[] data;

    /**
     * Creates new matrix initialized to the zero matrix
     */
    public Mat2f() {
        data = new float[4];
    }

    /**
     * Initialize to the identity matrix.
     */
    public void makeIdent() {<FILL_FUNCTION_BODY>}

    /**
     * Gets the (i,j)th element of this matrix, where i is the row
     * index and j is the column index
     */
    public float get(int i, int j) {
        return data[2 * i + j];
    }

    /**
     * Sets the (i,j)th element of this matrix, where i is the row
     * index and j is the column index
     */
    public void set(int i, int j, float val) {
        data[2 * i + j] = val;
    }

    /**
     * Set column i (i=[0..1]) to vector v.
     */
    public void setCol(int i, Vec2f v) {
        set(0, i, v.x());
        set(1, i, v.y());
    }

    /**
     * Set row i (i=[0..1]) to vector v.
     */
    public void setRow(int i, Vec2f v) {
        set(i, 0, v.x());
        set(i, 1, v.y());
    }

    /**
     * Transpose this matrix in place.
     */
    public void transpose() {
        float t = get(0, 1);
        set(0, 1, get(1, 0));
        set(1, 0, t);
    }

    /**
     * Return the determinant.
     */
    public float determinant() {
        return (get(0, 0) * get(1, 1) - get(1, 0) * get(0, 1));
    }

    /**
     * Full matrix inversion in place. If matrix is singular, returns
     * false and matrix contents are untouched. If you know the matrix
     * is orthonormal, you can call transpose() instead.
     */
    public boolean invert() {
        float det = determinant();
        if (det == 0.0f) {
            return false;
        }

        // Create transpose of cofactor matrix in place
        float t = get(0, 0);
        set(0, 0, get(1, 1));
        set(1, 1, t);
        set(0, 1, -get(0, 1));
        set(1, 0, -get(1, 0));

        // Now divide by determinant
        for (int i = 0; i < 4; i++) {
            data[i] /= det;
        }
        return true;
    }

    /**
     * Multiply a 2D vector by this matrix. NOTE: src and dest must be
     * different vectors.
     */
    public void xformVec(Vec2f src, Vec2f dest) {
        dest.set(get(0, 0) * src.x() +
                get(0, 1) * src.y(),

            get(1, 0) * src.x() +
                get(1, 1) * src.y());
    }

    /**
     * Returns this * b; creates new matrix
     */
    public Mat2f mul(Mat2f b) {
        Mat2f tmp = new Mat2f();
        tmp.mul(this, b);
        return tmp;
    }

    /**
     * this = a * b
     */
    public void mul(Mat2f a, Mat2f b) {
        for (int rc = 0; rc < 2; rc++) {
            for (int cc = 0; cc < 2; cc++) {
                float tmp = 0.0f;
                for (int i = 0; i < 2; i++) {
                    tmp += a.get(rc, i) * b.get(i, cc);
                }
                set(rc, cc, tmp);
            }
        }
    }

    public Matf toMatf() {
        Matf out = new Matf(2, 2);
        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 2; j++) {
                out.set(i, j, get(i, j));
            }
        }
        return out;
    }

    @Override
    public String toString() {
        String endl = System.getProperty("line.separator");
        return "(" +
            get(0, 0) + ", " + get(0, 1) + endl +
            get(1, 0) + ", " + get(1, 1) + ")";
    }
}

        for (int i = 0; i < 2; i++) {
            for (int j = 0; j < 2; j++) {
                if (i == j) {
                    set(i, j, 1.0f);
                } else {
                    set(i, j, 0.0f);
                }
            }
        }
    
<no_super_class>