}
            else {
                ObjectHandle oh = gcHeap.getObjectHandle(objectIndexOfIconThatCanBeDroppedUpon);

                // Clear the rectangle
                g.drawRect(oh.fish.getFishPosition().x, oh.fish.getFishPosition().y, oh.fish.getFishWidth(),
                    oh.fish.getFishHeight());

                // Clear the line between the nose of the from fish and the top of the tail of
                // of the to fish.
                g.drawLine(lineStart.x, lineStart.y, oh.fish.getFishPosition().x,
                    oh.fish.getFishPosition().y);

                mouseIsOverAnIconThatCanBeDroppedUpon = false;
            }
        }


        // Check to see if the line was dropped on a fish icon. If so,
        // connect the two fish by writing to the instance variable of the
        // class and repainting.
        for (int i = gcHeap.getHandlePoolSize() - 1; i >= 0; --i) {
            ObjectHandle oh = gcHeap.getObjectHandle(i + 1);
            if (!oh.free) {

                Point o = oh.fish.getFishPosition();
                if (x >= o.x && x < o.x + oh.fish.getFishWidth() && y >= o.y
                    && y < o.y + oh.fish.getFishHeight()) {

                    if (i + 1 == objectIndexOfFishIconThatWasClicked) {
                        // If they dropped on the same fish they started from, don't link.
                        break;
                    }

                    if (fishCanLink(fishIconThatWasClicked, oh.fish)) {
                        int offset = getInstanceVariableOffset(fishIconThatWasClicked, oh.fish);

                        // Set the clicked upon fish variable to equal the dropped upon
                        // fish object.
                        gcHeap.setObjectPool(fishObjectThatWasClicked.objectPos + offset, i + 1);
                        repaint();
                    }
                    break;
                }
            }
        }

        yellowLocalVarClicked = false;
        blueLocalVarClicked = false;
        redLocalVarClicked = false;
        iconClicked = false;

        return true;
    }

    public boolean mouseDrag(Event evt, int x, int y) {

        if (!iconClicked && !yellowLocalVarClicked && !blueLocalVarClicked
            && !redLocalVarClicked) {
            return true;
        }

        if (yellowLocalVarClicked || blueLocalVarClicked || redLocalVarClicked) {

            Graphics g = getGraphics();
            g.setColor(Color.blue);
            Color colorOfClickedLocalVar = Color.yellow;
            int xLineStart = xLocalVarRectStart + localVarRectWidth;
            int yLineStart = yYellowFishLocalVarStart + (localVarRectHeight / 2);
            if (blueLocalVarClicked) {
                colorOfClickedLocalVar = Color.cyan;
                yLineStart = yBlueFishLocalVarStart + (localVarRectHeight / 2);
            }
            else if (redLocalVarClicked) {
                colorOfClickedLocalVar = Color.red;
                yLineStart = yRedFishLocalVarStart + (localVarRectHeight / 2);
            }
            g.setXORMode(colorOfClickedLocalVar);

            if (!dragging) {
                dragging = true;
            }
            else {
                // Check to see if the mouse has left an icon that can be dropped upon. If
                // so, need to erase the outline rectangle and erase the line from the nose of
                // the "from" fish to top left corner of outline rectangle of "to" fish.
                if (mouseIsOverAnIconThatCanBeDroppedUpon) {
                    ObjectHandle oh = gcHeap.getObjectHandle(objectIndexOfIconThatCanBeDroppedUpon);
                    Point o = oh.fish.getFishPosition();
                    if (x < o.x || x >= o.x + oh.fish.getFishWidth() || y < o.y
                        || y >= o.y + oh.fish.getFishHeight()) {

                        g.drawRect(oh.fish.getFishPosition().x, oh.fish.getFishPosition().y, oh.fish.getFishWidth(),
                            oh.fish.getFishHeight());

                        // Draw a line between the nose of the from fish and the top of the tail of
                        // of the to fish.
                        g.drawLine(xLineStart, yLineStart, oh.fish.getFishPosition().x,
                            oh.fish.getFishPosition().y);

                        mouseIsOverAnIconThatCanBeDroppedUpon = false;
                    }
                }
                else {
                    // No drop-on-able fish is beneath the mouse, so erase the new line between
                    // the nose of the fromFish and the previous mouse position.
                    g.drawLine(xLineStart, yLineStart, currentMouseDragPosition.x, currentMouseDragPosition.y);
                }
            }

            // Check to see if a fish is beneath the mouse that can be dropped upon.
            for (int i = gcHeap.getHandlePoolSize() - 1; i >= 0; --i) {
                ObjectHandle oh = gcHeap.getObjectHandle(i + 1);
                if (!oh.free) {

                    Point o = oh.fish.getFishPosition();
                    if (x >= o.x && x < o.x + oh.fish.getFishWidth() && y >= o.y
                        && y < o.y + oh.fish.getFishHeight()) {

                        if (!mouseIsOverAnIconThatCanBeDroppedUpon) {

                            if (oh.fish.getFishColor() == colorOfClickedLocalVar) {
                                mouseIsOverAnIconThatCanBeDroppedUpon = true;
                            }

                            if (mouseIsOverAnIconThatCanBeDroppedUpon) {
                                objectIndexOfIconThatCanBeDroppedUpon = i + 1;
                                g.drawRect(oh.fish.getFishPosition().x, oh.fish.getFishPosition().y, oh.fish.getFishWidth(),
                                    oh.fish.getFishHeight());

                                // Draw a line between the nose of the from fish and the top of the tail of
                                // of the to fish.
                                g.drawLine(xLineStart, yLineStart, oh.fish.getFishPosition().x,
                                    oh.fish.getFishPosition().y);
                            }
                        }
                        break;
                    }
                }
            }

            if (!mouseIsOverAnIconThatCanBeDroppedUpon) {
                // No drop-on-able fish is beneath the mouse, so just draw the new line between
                // the nose of the fromFish and the current mouse position.
                g.drawLine(xLineStart, yLineStart, x, y);
            }
            currentMouseDragPosition.x = x;
            currentMouseDragPosition.y = y;

            g.setPaintMode();
            return true;
        }

        FishIcon fishIconThatWasClicked = gcHeap.getObjectHandle(objectIndexOfFishIconThatWasClicked).fish;
        Color colorOfClickedFish = gcHeap.getObjectHandle(objectIndexOfFishIconThatWasClicked).fish.getFishColor();

        // Don't start dragging unless the mouse has moved a threshold number of
        // pixels in x or y.
        if (!dragging) {
            int thresholdPixels = 5;
            Point iconOrigin = fishIconThatWasClicked.getFishPosition();
            int xOriginalClick = iconOrigin.x + posOfMouseInsideIconWhenFirstPressed.x;
            int yOriginalClick = iconOrigin.y + posOfMouseInsideIconWhenFirstPressed.y;
            int xDifference = x - xOriginalClick;
            if (xDifference < 0) {
                xDifference = 0 - xDifference;
            }
            int yDifference = y - yOriginalClick;
            if (yDifference < 0) {
                yDifference = 0 - yDifference;
            }
            if (xDifference < thresholdPixels && yDifference < thresholdPixels) {
                return true;
            }
        }

        Graphics g = getGraphics();
        g.setColor(Color.blue);
        g.setXORMode(colorOfClickedFish);

        Point fishNose = fishIconThatWasClicked.getFishNosePosition();

        if (!dragging) {
            dragging = true;
        }
        else {
            // Check to see if the mouse has left an icon that can be dropped upon. If
            // so, need to erase the outline rectangle and erase the line from the nose of
            // the "from" fish to top left corner of outline rectangle of "to" fish.
            if (mouseIsOverAnIconThatCanBeDroppedUpon) {
                ObjectHandle oh = gcHeap.getObjectHandle(objectIndexOfIconThatCanBeDroppedUpon);
                Point o = oh.fish.getFishPosition();
                if (x < o.x || x >= o.x + oh.fish.getFishWidth() || y < o.y
                    || y >= o.y + oh.fish.getFishHeight()) {

                    g.drawRect(oh.fish.getFishPosition().x, oh.fish.getFishPosition().y, oh.fish.getFishWidth(),
                        oh.fish.getFishHeight());

                    // Draw a line between the nose of the from fish and the top of the tail of
                    // of the to fish.
                    g.drawLine(fishNose.x, fishNose.y, oh.fish.getFishPosition().x,
                        oh.fish.getFishPosition().y);

                    mouseIsOverAnIconThatCanBeDroppedUpon = false;
                }
            }
            else {
                // No drop-on-able fish is beneath the mouse, so erase the new line between
                // the nose of the fromFish and the previous mouse position.
                g.drawLine(fishNose.x, fishNose.y, currentMouseDragPosition.x, currentMouseDragPosition.y);
            }
        }

        // Check to see if a fish is beneath the mouse that can be dropped upon.
        for (int i = gcHeap.getHandlePoolSize() - 1; i >= 0; --i) {
            ObjectHandle oh = gcHeap.getObjectHandle(i + 1);
            if (!oh.free) {

                Point o = oh.fish.getFishPosition();
                if (x >= o.x && x < o.x + oh.fish.getFishWidth() && y >= o.y
                    && y < o.y + oh.fish.getFishHeight()) {

                    if (!mouseIsOverAnIconThatCanBeDroppedUpon) {
                        if (i + 1 == objectIndexOfFishIconThatWasClicked) {
                            // If they are over the same fish they started from, don't
                            // draw a rectangle.
                            break;
                        }

                        mouseIsOverAnIconThatCanBeDroppedUpon = fishCanLink(fishIconThatWasClicked, oh.fish);
                        if (mouseIsOverAnIconThatCanBeDroppedUpon) {
                            objectIndexOfIconThatCanBeDroppedUpon = i + 1;
                            g.drawRect(oh.fish.getFishPosition().x, oh.fish.getFishPosition().y, oh.fish.getFishWidth(),
                                oh.fish.getFishHeight());

                            // Draw a line between the nose of the from fish and the top of the tail of
                            // of the to fish.
                            g.drawLine(fishNose.x, fishNose.y, oh.fish.getFishPosition().x,
                                oh.fish.getFishPosition().y);
                        }
                    }
                    break;
                }
            }
        }

        if (!mouseIsOverAnIconThatCanBeDroppedUpon) {
            // No drop-on-able fish is beneath the mouse, so just draw the new line between
            // the nose of the fromFish and the current mouse position.
            g.drawLine(fishNose.x, fishNose.y, x, y);
        }
        currentMouseDragPosition.x = x;
        currentMouseDragPosition.y = y;

        g.setPaintMode();
        return true;
    }

    private boolean fishCanLink(FishIcon fromFish, FishIcon toFish) {

        // Red fish can link with anything.
        if (fromFish.getFishColor() == Color.red) {
            return true;
        }

        // Blue fish can link with anything except red.
        if (fromFish.getFishColor() == Color.cyan) {
            if (toFish.getFishColor() != Color.red) {
                return true;
            }
            else {
                return false;
            }
        }

        // Yellow fish can only link with yellow fish.
        if (toFish.getFishColor() == Color.yellow) {
            return true;
        }

        return false;
    }

    // getInstanceVariableOffset returns the offset from the beginning of the "from" fish
    // object in the objectPool of the variable to which the "to" fish reference should
    // be assigned. The offset is in number of ints. This assumes that the toFish is
    // a valid fish color for the from fish, e.g., yellow fromFish will only have
    // yellow toFish. The fish objects are defined as:
    //
    // class RedFish {
    //      RedFish myFriend;
    //      BlueFish myLunch;
    //      YellowFish mySnack;
    // }
    //
    // class BlueFish {
    //      BlueFish myFriend;
    //      YellowFish myLunch;
    // }
    //
    // class YellowFish {
    //      YellowFish myFriend;
    // }
    //
    private int getInstanceVariableOffset(FishIcon fromFish, FishIcon toFish) {

        // Red fish can link with anything.
        if (fromFish.getFishColor() == Color.red) {
            if (toFish.getFishColor() == Color.red) {
                return 0;
            }
            else if (toFish.getFishColor() == Color.cyan) {
                return 1;
            }
            else {
                return 2; // yellow fish
            }
        }

        // Blue fish can link with anything except red.
        if (fromFish.getFishColor() == Color.cyan) {
            if (toFish.getFishColor() == Color.cyan) {
                return 0;
            }
            else {
                return 1; // yellow fish
            }
        }

        // Yellow fish can only link with yellow fish.
        return 0;
    }
    */
}