For jdt.ui
internal usage, here’s a list of helper classes that are frequently used:
org.eclipse.jdt.internal.corext.dom
:Bindings
ASTNodeFactory
ASTNodes
TypeRules
org.eclipse.jdt.internal.corext.refactoring.structure.ASTNodeSearchUtil
org.eclipse.jdt.internal.corext.codemanipulation.StubUtility
org.eclipse.jdt.internal.corext.codemanipulation.StubUtility2
org.eclipse.jdt.internal.ui.text.correction.ASTResolving
org.eclipse.jdt.ui.CodeGeneration
org.eclipse.jdt.internal.corext.util.JavaModelUtil
org.eclipse.jdt.internal.corext.refactoring.util.JavaElementUtil