Bug 4240 Can't edit class path entry (1GKEPIF)
There is no way to edit an existing entry for a library on the Java Build Path project properties page (other than editing the .classpath file directly). NOTES: EG (9/22/2001 11:42:11 AM) this is particularly annoying for variables. we should have an Edit button when a variable is selected.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/NewVariableEntryDialog.java
boolean canExtend= false;
		
		if (nSelected > 0) {
			fResultPaths= new Path[nSelected];
			for (int i= 0; i < nSelected; i++) {
				CPVariableElement curr= (CPVariableElement) selected.get(i);
				fResultPaths[i]= new Path(curr.getName());
				if (!curr.getPath().toFile().isFile()) {
					isValidSelection= false;
				}
					
			}
		} else {
			isValidSelection= false;
		}
		fExtensionButton.setEnabled(nSelected == 1 && !isValidSelection);
		fOkButton.setEnabled(isValidSelection);
	}
	
	private IPath[] chooseExtensions(CPVariableElement elem) {
		File file= elem.getPath().toFile();
		ILabelProvider lp= new FileLabelProvider();
		ITreeContentProvider cp= new FileContentProvider();
		ElementTreeSelectionDialog dialog= new ElementTreeSelectionDialog(getShell(), lp, cp);
		dialog.setTitle(NewWizardMessages.getString("NewVariableEntryDialog.ExtensionDialog.title")); 
		dialog.setMessage(NewWizardMessages.getFormattedString("NewVariableEntryDialog.ExtensionDialog.description", elem.getName())); 
		dialog.setInput(file);
		if (dialog.open() == dialog.OK) {
			Object[] selected= dialog.getResult();
			IPath[] paths= new IPath[selected.length];