Matrix multiplication using arrays

Question

Utilizing multidimensional arrays, I'm attempting to create a straightforward matrix multiplication approach ([2][2]). Being rather new at this, I'm unable to identify my mistakes. Please let me know what it is if you can; I'd really appreciate it. Since I'm basically doing this to learn how it works, I'd prefer not to use libraries or anything similar. 

My variable declaration is as follows:

Double[][] A={{4.00,3.00},{2.00,1.00}}; 
Double[][] B={{-0.500,1.500},{1.000,-2.0000}};

A*B should return the identity matrix. But it won't work. This is the code:

public static Double[][] multiplicar(Double[][] A, Double[][] B){
    Double[][] C= new Double[2][2];
    int i,j;

    for(i=0;i<2;i++) {
        for(j=0;j<2;j++){
            C[i][j]=0.00000;
        }
    } 

    for(i=0;i<2;i++){
        for(j=0;j<2;j++)
            C[i][j]+=(A[i][j]*B[j][i]);
    }
    return C;
}