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2. Extend the logging package to support a null device in which messages
are thrown away.
3. Continuing from Exercise 1, introduce the following matrix-multiplication
method into Matrix :
Matrix multiply(Matrix m)
{
Matrix
result
=
new
Mat-
rix(matrix.length, matrix[0].length);
for (int i = 0; i < matrix.length;
i++)
for
(int
j
=
0;
j
<
m.matrix[0].length; j++)
for
(int
k
=
0;
k
<
m.matrix.length; k++)
result.matrix[i][j]
=
result.matrix[i][j]+
mat-
rix[i][k]*m.matrix[k][j];
return result;
}
Next,declarea void rotate(double angle) methodin G2D .This
wiserotation),whichspecifiesarotationangleindegrees.Itthencreatesa
3-by-3rotation Matrix andinitializesthefollowing(row,column)entries:
(0, 0) to the cosine of the angle, (1, 0) to the sine of the angle, (0, 1) to
the negative of the angle's sine, (1, 1) to the cosine of the angle, and (2,
2)to1.0.Staticallyimportallnecessary Math classmethods.Finally, ro-
tate() multipliestheidentitymatrixcreatedin G2D 'sconstructorbythis
rotation matrix, and invokes dump() to dump the result. Test rotate()
from the main() method by executing G2D g2d = new G2D();
g2d.rotate(45); . You should observe the following output:
1.0 0.0 0.0
0.0 1.0 0.0
0.0 0.0 1.0
0.7071067811865476 0.7071067811865475 0.0
-0.7071067811865475 0.7071067811865476 0.0
0.0 0.0 1.0
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