import javax.swing.*;

public class Main{
	public static void main(String[] args){
		//double[][] n = new double[100][100];
		//int m = 30;
		int n = 50;
		SparseMatrix mat = new SparseMatrix(n);
		GlesMatrisVy vy = new GlesMatrisVy(mat);
		Knappar knapp = new Knappar(mat,vy);
		JFrame f = new JFrame();
		f.add(vy, "North");
		f.add(knapp, "South");
		f.setVisible(true);
		f.pack();
		f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	}
}

------------------------------

import java.util.*;

public class SparseMatrix{
	private ArrayList<Triple> elem = new ArrayList<Triple>();
	private int nz, dim;

	private class Triple{
		int rad, col;
		double el;
		public Triple(int r, int c, double e){
			rad = r; col = c; el = e;
		}
	}

	public SparseMatrix(){}
	
	public SparseMatrix(int n){
		dim = n; 
	}

	public SparseMatrix(double[][] matrix, int nz){
		dim = matrix.length;
		this.nz = nz;
		for(int i=0; i<dim; i++){
			for(int j=0; j<dim; j++){
				if(matrix[i][j] != 0){
					elem.add(new Triple(i,j,matrix[i][j]));
				}
			}
		}
	}

	public int getDim(){
		return dim;
	}

	public int nnz(){
		return nz;
	}

	public double elemAt(int r, int c){
		Triple arrayElement;
		double retElementValue = 0;
		int arraySize = elem.size();
		
//		Look at the class definition of Trippel
//		The row , column and value can be retrieved by using
//		the instance variables .rad .col .el
		
		for(int i=0;i<arraySize;i++){
				arrayElement = elem.get(i);
				if (arrayElement.rad == r && arrayElement.col == c){
					retElementValue = arrayElement.el;
				}
			}		
		return retElementValue;
	}


	public boolean symmetric(){
		if(nz%2 != 0)
			return false;
		int ok = 0;
		for(int i=0; i<nz; i++){
			Triple t = elem.get(i);
			Triple nt = new Triple(t.col, t.rad, t.el);
			if(elem.contains(nt)) // returnerar true ifall elem innehåller trippeln nt
				ok++;
		}
		return ok==nz;
	}

	public void addElem(int r, int c, double e){
		if(e != 0){
			elem.add(new Triple(r,c,e));
			nz++;
		}
		if(dim<r) dim = r;
		if(dim<c) dim = c;	
	}

	public SparseMatrix mul(SparseMatrix mat){
		SparseMatrix ret = new SparseMatrix(mat.getDim());
		for(int i=0; i<dim; i++){
			for(int j=0; j<dim; j++){
				double e = 0;
				for(int k=0; k<dim; k++){
					e = e + elemAt(i,k) * mat.elemAt(k,j);
				ret.addElem(i,j,e);
				}
			}
		}
		return ret;
	}
}

------------------------------

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;

public class GlesMatrisVy extends JPanel{
	private SparseMatrix mod;
	private final int SIZE = 4;

	public GlesMatrisVy( SparseMatrix m ){
		mod = m;
		addMouseListener( new Lyss() );
		setPreferredSize( new Dimension( SIZE * mod.getDim(), SIZE * mod.getDim() ) );
	}

	public void PaintComponent(Graphics g){
		super.paintComponent(g);
		g.setColor(Color.RED);

		for( int i=0; i<mod.getDim(); i++ ){
			for( int j=0; j<mod.getDim(); j++ ){
				if( mod.elemAt(i,j) != 0 ){
					g.fillOval( j*SIZE, i*SIZE, SIZE, SIZE );
				}
			}

		}
	}

	public void bytModell( SparseMatrix m ){
		mod = m;	
	}

	class Lyss extends MouseAdapter{
		public void mouseClicked( MouseEvent e ){
			int y = e.getY()/SIZE;
			int x = e.getX()/SIZE;
			if( mod.elemAt(x,y) == 0 ){
				double elem = Double.parseDouble(JOptionPane.showInputDialog( "Elem at row " + y + " and col " + x + "?" ));
				mod.addElem(y,x,elem);
				repaint();
			}
		}
	}
}

--------------------------

import java.awt.event.*;
import javax.swing.*;
import java.awt.*;
	
public class Knappar extends JPanel implements ActionListener{
	private SparseMatrix mod;
	GlesMatrisVy vy;
	JButton knapp = new JButton("Multiplicate");
	public Knappar(SparseMatrix m, GlesMatrisVy v){
		mod = m;
		vy = v;
		knapp.addActionListener(this);
		add(knapp);
	}
	
	
		public void actionPerformed(ActionEvent e){
			mod = mod.mul(mod);
			vy.bytModell(mod);
			vy.repaint();
		}
}