[英]java arraylist null pointer exception when adding
Could someone please help me understand why i'm getting a null pointer when adding to my array list.有人可以帮我理解为什么我在添加到我的数组列表时得到一个空指针。 Im trying to make it so that it will change the text on a button when it is clicked, however my ArrayList
does not seem to be adding the things into it?我试图让它在单击按钮时更改按钮上的文本,但是我的ArrayList
似乎没有将内容添加到其中?
public class Game {
private GUI gui;
private ArrayList<String> pairs;
boolean clicked;
public Game() {
gui = new GUI(this);
clicked = false;
ArrayList<String> pairs = new ArrayList<String>();
}
public void addPairs() {
pairs.add("dog"); // where i get the null pointer
pairs.add("dog");
}
You should initialize the class member pairs
您应该初始化类成员pairs
this.pairs = new ArrayList<>(); // this may be omitted
instead of creating a new local list而不是创建一个新的本地列表
ArrayList<String> pairs = new ArrayList<String>();
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