public static void renameType(IType type, String newName) {
	final RefactoringContribution contribution = RefactoringCore
			.getRefactoringContribution(IJavaRefactorings.RENAME_TYPE);
	final RenameJavaElementDescriptor descriptor = (RenameJavaElementDescriptor) contribution.createDescriptor();
	descriptor.setProject(type.getResource().getProject().getName());
	descriptor.setJavaElement(type);
	descriptor.setNewName(newName);
		final RefactoringStatus status = new RefactoringStatus();
	try {
		final Refactoring refactoring = descriptor.createRefactoring(status);
		final IProgressMonitor monitor = new NullProgressMonitor();
		refactoring.checkInitialConditions(monitor);
		refactoring.checkFinalConditions(monitor);
		final Change change = refactoring.createChange(monitor);
		change.perform(monitor);
	} catch (final Exception e) {
		e.printStackTrace();
	}
}

IType javaTypeToRename = ...
renameType(javaTypetoRename, "ChangedTypeName");