public void selectNext() {

		if (null == completionData) {
			return;
		}
		for (int i = jlist.getSelectedIndex() + 1; i < completionData.size(); i++) {
			CodeCompletion completion = completionData.get(i);
			if (CodeCompletion.isValid(completion)) {
				jlist.setSelectedIndex(i);
				jlist.ensureIndexIsVisible(i);
				break;
			}
		}
	}
Selects the next item in the list with a usable completion.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/interpreter/CodeCompletionWindow.java