NullPointerException when I try to output get method [duplicate]

This question already has an answer here:

• What is a NullPointerException, and how do I fix it? 12 answers

I have an ArrayList of Question Class objects and I need to output the random selected question in a JSF page. everithing seems OK but when I run it, gives me a java lang nullpointerException

public class GameBean implements Serializable {

private Random random;
private String question; 
private String answer;
//above are the attributes

METHOD

public Question getQuestion() {
int index = random.nextInt(questionList.size());
Question q = questionList.get(index);

return q;}

JSF

<h:outputLabel value="#{GameBean.question}" />