Numbers - Java - page 200

Solution

Use the following code as a model.

Discussion

It is straightforward to multiply an array of a numeric type. The code in Example 5-5 imple-
ments matrix multiplication.

Example 5-5. Matrix.java
public public class class Matrix Matrix {

/* Matrix-multiply two arrays together.
* The arrays MUST be rectangular.
* @author Tom Christiansen & Nathan Torkington, Perl Cookbook version.
*/
public

public static static int int [][] multiply ( int int [][] m1 , int int [][] m2 ) {

int int m1rows = m1 . length ;

int int m1cols = m1 [ 0 ]. length ;

int

int m2rows = m2 . length ;
int

int m2cols = m2 [ 0 ]. length ;
iif ( m1cols != m2rows )
throw throw new new IllegalArgumentException (

"matrices don't match: " + m1cols + " != " + m2rows );

int int [][] result = new new int int [ m1rows ][ m2cols ];

// multiply
for for ( int int i = 0 ; i < m1rows ; i ++) {

for

for ( int int j = 0 ; j < m2cols ; j ++) {

for

for ( int int k = 0 ; k < m1cols ; k ++) {

result [ i ][ j ] += m1 [ i ][ k ] * m2 [ k ][ j ];

}

}

}

return return result ;

}

/** Matrix print.
*/
public public static static void void mprint ( int int [][] a ) {

int int rows = a . length ;

int int cols = a [ 0 ]. length ;

System . out . println ( "array[" + rows + "][" + cols + "] = {" );