class Matrix {

    public Matrix multiply(Matrix by){
        Matrix rslt = new Matrix();
        
        float[] a = vals;
        float[] b = by.vals;
        float[] c = rslt.vals;
        
        c[I11] = a[I11]*b[I11] + a[I12]*b[I21] + a[I13]*b[I31];  
        c[I12] = a[I11]*b[I12] + a[I12]*b[I22] + a[I13]*b[I32]; 
        c[I13] = a[I11]*b[I13] + a[I12]*b[I23] + a[I13]*b[I33]; 
        c[I21] = a[I21]*b[I11] + a[I22]*b[I21] + a[I23]*b[I31];  
        c[I22] = a[I21]*b[I12] + a[I22]*b[I22] + a[I23]*b[I32]; 
        c[I23] = a[I21]*b[I13] + a[I22]*b[I23] + a[I23]*b[I33]; 
        c[I31] = a[I31]*b[I11] + a[I32]*b[I21] + a[I33]*b[I31];  
        c[I32] = a[I31]*b[I12] + a[I32]*b[I22] + a[I33]*b[I32]; 
        c[I33] = a[I31]*b[I13] + a[I32]*b[I23] + a[I33]*b[I33]; 
        
        return rslt;
    }

    public  Matrix();
    public  Matrix(float tx, float ty);
    public  Matrix(float a, float b, float c, float d, float e, float f);

}