Bug 31395 Child window of Preferences dialog centers between screens
On the Preferences->Java->Code Generation->Names tab, the Edit button opens a dialog that is split between multiple monitors, instead of centering on the main Preference window like the rest of its child windows do.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/preferences/OptionsConfigurationBlock.java
protected void doFullBuild() {
		ProgressMonitorDialog dialog= new ProgressMonitorDialog(getShell());
		try {
			dialog.run(true, true, new IRunnableWithProgress() {
				public void run(IProgressMonitor monitor) throws InvocationTargetException {
					try {
						if (fProject != null) {
							fProject.getProject().build(IncrementalProjectBuilder.FULL_BUILD, monitor);
						} else {
							JavaPlugin.getWorkspace().build(IncrementalProjectBuilder.FULL_BUILD, monitor);
						}
					} catch (CoreException e) {
						throw new InvocationTargetException(e);
					}
				}
			});
		} catch (InterruptedException e) {
			
		} catch (InvocationTargetException e) {
			String title= PreferencesMessages.getString("OptionsConfigurationBlock.builderror.title"); 
			String message= PreferencesMessages.getString("OptionsConfigurationBlock.builderror.message"); 
			ExceptionHandler.handle(e, getShell(), title, message);
		}
	}		
	
	public void performDefaults() {
		fWorkingValues= getDefaultOptions();
		updateControls();
		validateSettings(null, null);