public abstract class Matrix {
	//Data - number of rows and columns
    protected int n;  // number of rows
    protected int m;  // number of columns
    
    //Abstract methods
    public abstract double elementAt(int i,int j);
    public abstract double setElementAt(int i,int j,double value);
    protected abstract Matrix create(int rows,int cols);
    
    //Protected method
    protected int f(int i,int j) {
		if (i<1 || i>n || j<1 || j>m) 
          	throw new IndexOutOfBoundsException("Incorrect indexes!");
        return -1;
	}
	          	
    //Public methods
    public int getRows(){ return n; }
    
    public int getColumns(){ return m; }    
    
    public Matrix add(Matrix B) {
        Matrix A = this;
        if (B.n != A.n || B.m != A.m)
        	throw new RuntimeException("Illegal matrix dimensions!");
        Matrix C = create(n,m);
        for (int i = 1; i <= n; i++)
            for (int j = 1; j <= m; j++)
                C.setElementAt(i,j,A.elementAt(i,j) + B.elementAt(i,j));
        return C;
    }
    
	public Matrix mult(Matrix B) {
		System.out.println("Not implemented!"); return null;
	}
	
	public Matrix mult(double value) {
		System.out.println("Not implemented!"); return null;
	}
	
	public Matrix transpose() {
		System.out.println("Not implemented!"); return null;
	}
	
	public boolean equals(Object obj) {
		Matrix B=(Matrix)obj;
		System.out.println("Not implemented!"); return false;
	}
}