移动网格nullpointer异常

Question

我正在尝试允许通过网格移动并使用字符串显示我当前的位置。如果我在a1上并输入＆＃39; down＆＃39;我将在b1。 （我是java的新手。）

          public class ClassMethodtest {

/**
 * @param args the command line arguments
 */
public static void main(String[] args) {

    Scanner replay = new Scanner(System.in);

    String answer;



   do{ 
      MoveClass newMoveClass = new MoveClass();

     newMoveClass.MoveAround();

     newMoveClass.Location();

            System.out.println("move again?");

    answer = replay.next();


   } while(answer.equals("yes"));
}




public class MoveClass {

private final String array[] = {"A1", "A2", "A3", "A4", "B1", "B2", "B3", "B4", 
                         "C1", "C2", "C3", "C4", "D1", "D2", "D3", "D4"};
private final Scanner kb = new Scanner(System.in);    

private String location; 


public void MoveAround(){

    System.out.println("move nigga");
    String answer = kb.next();

   switch (location) {
       case "A1":
           if(answer.equals("down")){
               location = array[4];
           }
           else if(answer.equals("right")){
               location = array[1];
           }  break;
           //etc.....

这会引发空指针异常，我不明白为什么。

Answer 1

private String location; 

位置为空。你需要设置初始位置，如：

private String location = array[6];