Bug 276202 [Forms] NPE if dispose() called on FormToolkit more than once
Build id: I20090512-2000 java.lang.NullPointerException at org.eclipse.ui.forms.widgets.FormToolkit.dispose(FormToolkit.java:711) At the moment, if you invoke dispose() twice on a FormToolkit instance, an NPE will be thrown. public void dispose() { if (colors.isShared() == false) { colors.dispose(); colors = null; } boldFontHolder.dispose(); } As can be seen, the 'colors' field is set to 'null' which is the cause of the NPE. It's okay to repeatedly invoke dispose() on an SWT widget so I feel this pattern should be extended for a FormToolkit also.
bundles/org.eclipse.ui.forms/src/org/eclipse/ui/forms/widgets/FormToolkit.java
form.setSeparatorVisible(true);
	}
	/**
	 * Creates a scrolled page book widget as a part of the form.
	 * 
	 * @param parent
	 *            the page book parent
	 * @param style
	 *            the text style
	 * @return the scrolled page book widget
	 */
	public ScrolledPageBook createPageBook(Composite parent, int style) {
		ScrolledPageBook book = new ScrolledPageBook(parent, style
				| orientation);
		adapt(book, true, true);
		book.setMenu(parent.getMenu());
		return book;
	}
	/**
	 * Disposes the toolkit.
	 */
	public void dispose() {
		if (colors.isShared() == false) {
			colors.dispose();
			colors = null;
		}
		boldFontHolder.dispose();
	}
	/**
	 * Returns the hyperlink group that manages hyperlinks for this toolkit.