Java ArrayList中的安卓 NullPointerException

Question

我这辈子都搞不清楚！ 它说第20行有一个空指针异常，就是这一行

walls.add(new Wall(random.nextInt(20), random.nextInt(20)));

我申报错了吗？我做错了什么？这是不是其中的一件事，它是如此愚蠢，以至于我只是瞎了眼

以下是完整的代码：

package com.astar.world;

import java.util.ArrayList;
import java.util.List;
import java.util.Random;

import com.astar.objects.Player;
import com.astar.objects.Wall;

public class World {

private Player player;
private List<Wall> walls;
private Random random;

public World() {
    player = new Player(2, 2);
    walls = new ArrayList<Wall>();
    for (int i = 0; i < 10; i++) {
        walls.add(new Wall(random.nextInt(20), random.nextInt(20)));
    }
}

public void update(float deltaTime) {

}

public Player getPlayer() {
    return player;
}

public List<Wall> getWalls() {
    return walls;
}

}

以下是错误：

Exception in thread "LWJGL Application" java.lang.NullPointerException at com.astar.world.World.(World.java:20) at com.astar.screens.GameScreen.(GameScreen.java:13) at com.astar.game.AStarAlgoGame.create(AStarAlgoGame.java:11) at com.badlogic.gdx.backends.lwjgl.LwjglApplication.mainLoop(LwjglApplication.java:136) at com.badlogic.gdx.backends.lwjgl.LwjglApplication$1.run(LwjglApplication.java:114)

Answer 1

我没有看到您在代码中实例化变量random