- Java code
import java.awt.*;import javax.swing.*;class Astar extends JPanel { int[][] map = { {1,1,0,0,0,0,0,0,0,0}, {1,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,1,1,1,1,1,0,0}, {0,0,0,0,0,0,0,1,0,0}, {0,0,0,0,0,0,0,1,0,0}, {0,0,0,0,0,0,0,1,0,0}, {1,1,1,0,0,0,0,0,0,0}, {1,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,1,1,0,0}, }; Cell[][] map1; public Astar(){ map1 = new Cell[10][10]; for(int i=0;i<10;i++) for(int j=0;j<10;j++) map1[i][j].value = map[i][j]; JFrame f = new JFrame(); f.setBounds(100,100,600,500); f.add(this); f.setVisible(true); } public void paintComponent(Graphics g){ for(int i=0;i<10;i++){ for(int j=0;j<10;j++){ if(map[i][j]==0){ g.draw3DRect(40*j,40*i,40,40,true); g.drawString(map1[i][j].toString1(),40*j,40*i); } else if(map[i][j]==1) g.fill3DRect(40*j,40*i,40,40,true); } } } public static void main(String args[]){ new Astar(); } class Cell{ int value; boolean seen; boolean open; int direction; Cell(){ seen = true; open = true; } public String toString1(){ if(open) return "Open"; else return "Closed"; } }}------解决方案--------------------
for(int i=0;i<10;i++)
for(int j=0;j<10;j++)
{
map1[i][j]= new Cell();
map1[i][j].value = map[i][j];
}
------解决方案--------------------
虽然map1 = new Cell[10][10];你初始化了一个二维Cell数组，但是你并没有对里面的每个Cell进行初始化，所以默认初始化值为null，用null来调用value，所以就报错了
------解决方案--------------------
空指针就是 xx.xx .前面的那个值为null； 比较好找
------解决方案--------------------
正解！
------解决方案--------------------
数组默认是每个值都是null