Bug 219901 [Undo] new file creation subjec to Undo (file deleted without warning)
when creating a new file by right clicking on your project in the project explorer new->file this action is put on the undo/redo stack. Pressing Ctrl-Z to undo this action will thus delete your file. As this stack is separate from the stack in the editor , one can create a new file, work for a long time, then inadvertently press ctrl-z to undo a code change while having the focus on the project explorer and irrevocably lose their file. Redo will create a new EMPTY file; the work is gone, forever. This appears to only work for the "new file", not for "new->source file" etc. Although some may perceive this as a feature, it is hard to imagine a scenario where ctrl-z should permanently delete a file without warning.
bundles/org.eclipse.ui.ide/src/org/eclipse/ui/wizards/newresource/BasicNewProjectResourceWizard.java
IPerspectiveDescriptor finalPersp = reg
				.findPerspectiveWithId(finalPerspId);
		if (finalPersp != null && finalPersp instanceof IPluginContribution) {
			IPluginContribution contribution = (IPluginContribution) finalPersp;
			if (contribution.getPluginId() != null) {
				IWorkbenchActivitySupport workbenchActivitySupport = PlatformUI
						.getWorkbench().getActivitySupport();
				IActivityManager activityManager = workbenchActivitySupport
						.getActivityManager();
				IIdentifier identifier = activityManager
						.getIdentifier(WorkbenchActivityHelper
								.createUnifiedId(contribution));
				Set idActivities = identifier.getActivityIds();
				if (!idActivities.isEmpty()) {
					Set enabledIds = new HashSet(activityManager
							.getEnabledActivityIds());
					if (enabledIds.addAll(idActivities)) {
						workbenchActivitySupport
								.setEnabledActivityIds(enabledIds);
					}
				}
			}
		} else {
			IDEWorkbenchPlugin.log("Unable to find persective " 
					+ finalPerspId
					+ " in BasicNewProjectResourceWizard.updatePerspective"); 
			return;
		}