import java.awt.*;
import java.awt.event.*;

public class MouseClickDistanceFrame extends Frame
{
    private static final int FrameWidth  = 400;
    private static final int FrameHeight = 400;

    private Label clickDistanceLabel;

    private int startingX;
    private int startingY;
    private int endingX;
    private int endingY;

    public MouseClickDistanceFrame()
    {
        setTitle( "I'll measure the distance between your clicks..." );
        setSize ( FrameWidth, FrameHeight );

        clickDistanceLabel = new Label( "You have not clicked yet." );
        add( "North", clickDistanceLabel );

        startingX = 0;
        startingY = 0;
        endingX   = 0;
        endingY   = 0;

        addMouseListener( new MouseClickDistance() );
    }

    public void paint( Graphics g )
    {
        Color originalColor = g.getColor();
        g.setColor( Color.blue );
        g.drawLine( startingX, startingY, endingX, endingY );
        g.setColor( originalColor );
    }

    protected void update( double newDistance )
    {
        clickDistanceLabel.setText( "Distance = " + newDistance );
        repaint();
    }

    private class MouseClickDistance implements MouseListener
    {
        public void mousePressed( MouseEvent e )
        {
            startingX = e.getX();
	    startingY = e.getY();
        }

        public void mouseReleased( MouseEvent e )
        {
            endingX = e.getX();
	    endingY = e.getY();

            double distanceBetweenDownAndUp =
                      Math.sqrt( Math.pow( endingX - startingX, 2) +
                                 Math.pow( endingY - startingY, 2) );
            update( distanceBetweenDownAndUp );
        }

        public void mouseClicked ( MouseEvent e ) {}
        public void mouseEntered ( MouseEvent e ) {}
        public void mouseExited  ( MouseEvent e ) {}
    }
}