Bug 64298 JAR files already in build path still shown when adding JARs.
When adding JARs to the Java build path in 3.0M9, the JAR's that are already added do not get filtered out anymore like with all previous builds (M8 and lower). Instead, the complete list of all available JARs is shown.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/wizards/buildpaths/LibrariesWorkbookPage.java
public boolean hasChildren(TreeListDialogField field, Object element) {
			return getChildren(field, element).length > 0;
		}		
			
		
	
		public void dialogFieldChanged(DialogField field) {
			libaryPageDialogFieldChanged(field);
		}
	}
	
	private void libaryPageCustomButtonPressed(DialogField field, int index) {
		CPListElement[] libentries= null;
		switch (index) {
		case IDX_ADDJAR: 
			libentries= openJarFileDialog(null);
			break;
		case IDX_ADDEXT: 
			libentries= openExtJarFileDialog(null);
			break;
		case IDX_ADDVAR: 
			libentries= openVariableSelectionDialog(null);
			break;
		case IDX_ADDLIB: 
			libentries= openContainerSelectionDialog(null);
			break;
		case IDX_ADDFOL: 
			libentries= openClassFolderDialog(null);
			break;			
		case IDX_EDIT: