我需要做一个棋盘游戏,我从数组的左下角开始 [3][0] "大熊座"。 当我向西移动时,我得到一个 NullPointerException。我还需要一些帮助,沿对角线移动到 [2][1] "东北",但不确定如何为其编写代码。任何帮助将不胜感激。
//Declare Variables
Map map;
String input;
Scanner scan;
int row, col;
//Initialize Varibales
map = new Map();
scan = new Scanner(System.in);
row = 3; col = 0;
//Begin user dialog
System.out.println("Welcome to the Great Cal Poly Underground");
input ="";
while(!input.equals("quit"))
{
System.out.println(map.rooms[row][col].name);
System.out.print(">");
input = scan.nextLine().toLowerCase();
if (input.equals("w"))
{ if(map.rooms[row][col].isValidExit("w"))
col--;
else
System.out.println("You cant go that way");
}
else
if (input.equals("e"))
{ if(map.rooms[row][col].isValidExit("e"))
col++;
else
System.out.println("You cant go that way");
}
这是我的用户界面,这是我的地图
Room[][] rooms = new Room[4][4];
Map()
{
Room lectureHall = new Room();
Room cafeteria = new Room();
lectureHall.name = "Ursa Major";
lectureHall.exits = new String []{"e"};//can add north south west
cafeteria.name = "Los Olivos";
cafeteria.exits = new String []{"w"}; // can add north south east
rooms[3][0] = lectureHall;
rooms[2][1] = cafeteria;
这是我的房间
boolean isValidExit(String anExit)
{
boolean result = false;
int index = 0;
while (result == false && index < exits.length)
{
if(exits[index].equals(anExit))
result = true;
index++;
}
return result;
rooms
有 16 个引用,但只设置了两个 ( rooms[3][0] = lectureHall; rooms[2][1] = cafeteria;
)。您需要为其余索引创建对象。
像这样在 Java 中初始化数组:
Room[][] rooms = new Room[4][4];
仅初始化rooms
数组,这意味着只有数组不会为空。
但是,它"内部"的任何对象都不会初始化。
如果您希望急切地创建房间,然后设置其属性,请执行以下操作:
Room[][] rooms = new Room[4][4];
for (int i = 0; i < 4; i++) {
for (int j = 0; j < 4; j++) {
rooms[i][j] = new Room(...);
}
}
考虑上面的所有答案,而且,你的起始单元格是房间[3][0],如果你想去"西",你正在递减
col变量:if (input.equals("w"))
{ if(map.rooms[row][col].isValidExit("w"))
//you are decrementing col, which will become -1 after decrementing
col--;
else
System.out.println("You cant go that way");
}
然后程序回到循环到开头,在那里你显示当前房间的名称:
while(!input.equals("quit"))
{
System.out.println(map.rooms[row][col].name);
System.out.print(">");
由于 col = -1,您正在尝试执行 map.rooms[3][-1],这肯定会导致异常。
确保您没有引用<0 的数组索引。