我试图通过Java图形程序制作一个简单的四个tic-tac-toe板的图像.我的程序编译并可以运行,但不会生成四个板的图像.我的交互窗格中出现此错误(我使用DrJava进行编码):
Welcome to DrJava. Working directory is C:\Users\Daniel\Desktop\CS Programs
> run TicTacToeBoards
java.lang.NullPointerException
at TicTacToeBoards.drawTicTacToeBoard(TicTacToeBoards.java:38)
at TicTacToeBoards.<init>(TicTacToeBoards.java:18)
at TicTacToeBoards.main(TicTacToeBoards.java:52)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.runCommand(JavacCompiler.java:272)
这是我试图运行的程序:
import java.awt.Color;
public class TicTacToeBoards {
private NsccWindow win;
public TicTacToeBoards() {
NsccWindow win;
win = new NsccWindow(10, 10, 330, 300);
win.setTitle("Tic-Tac-Toe Boards");
drawTicTacToeBoard(40, 40);
drawTicTacToeBoard(40, 170);
drawTicTacToeBoard(170, 40);
drawTicTacToeBoard(170, 170);
}
public void drawTicTacToeBoard(int x, int y) {
NsccLine vertLineL;
NsccLine vertLineR;
NsccLine horizLineU;
NsccLine …