A DESCRIPTION OF THE REQUEST :
JScrollPane calls setViewport() on a JViewport that does not yet have an associated view Component, so the resulting call to JViewport.getView() always throws an ArrayIndexOutOfBoundsException.

The fix is simple: both the JScrollPane constructor and its setViewportView() method should initalise the JViewport's view before calling setViewport().

// this is the modified constructor
    public JScrollPane(Component view, int vsbPolicy, int hsbPolicy)
    {
setLayout(new ScrollPaneLayout.UIResource());
        setVerticalScrollBarPolicy(vsbPolicy);
        setHorizontalScrollBarPolicy(hsbPolicy);
        if (view != null) {
            setViewportView(view);
        }
setVerticalScrollBar(createVerticalScrollBar());
setHorizontalScrollBar(createHorizontalScrollBar());
setOpaque(true);
        updateUI();

if (!this.getComponentOrientation().isLeftToRight()) {
viewport.setViewPosition(new Point(Integer.MAX_VALUE, 0));
}
    }

// this is the modified mutator for the JScrollPane's view Component
    public void setViewportView(Component view) {
        if (getViewport() == null) {
            JViewport port = createViewport();
            if (view != null) {
                port.setView(view);
            }
            setViewport(port);
            return;
        }
        getViewport().setView(view);
    }

JUSTIFICATION :
Exceptions are an inefficient way to detect error situations; it is worse when a standard use of Swing causes exceptions to be thrown every time, even if they are caught internally.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Swing should use it's own API's in a way that don't trigger exceptions. This is more efficient (faster, which Swing needs to be) and it makes it easier to debug application code.