For jdt.ui internal usage, here’s a list of helper classes that are frequently used:
org.eclipse.jdt.internal.corext.dom:BindingsASTNodeFactoryASTNodesTypeRules
org.eclipse.jdt.internal.corext.refactoring.structure.ASTNodeSearchUtilorg.eclipse.jdt.internal.corext.codemanipulation.StubUtilityorg.eclipse.jdt.internal.corext.codemanipulation.StubUtility2org.eclipse.jdt.internal.ui.text.correction.ASTResolvingorg.eclipse.jdt.ui.CodeGenerationorg.eclipse.jdt.internal.corext.util.JavaModelUtilorg.eclipse.jdt.internal.corext.refactoring.util.JavaElementUtil

