キャンバスに描画しようとするとnullpointerexceptionエラーが発生する

Question

2次元配列を使用し、配列位置から読み取る文字に基づいて現在の座標に10x10ピクセルブロックを描画することにより、チェッカーボードパターンを本質的に描画しようとしています。私は、これが問題に関連するすべてのコードだと思う：

public void paint(Graphics g) { 
     super.paint(g); 
     Graphics2D g2d = (Graphics2D) g; 
     g.fillRect(0, 0, this.getWidth(),this.getHeight()); 
     for(int x = 0;x<=3;x++){ 
      for(int y = 0;y<=3;y++){ 
           // NPE occurs on this line: 
       if (globalmap[x][y] == '1'){g2d.fillRect(10*y, 10*x, 10,10);} 
      } 
     } 
} 

これは、マップ配列である：

0000 
0011 
0100 
0000 

スタックトレース：

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException 
     at com.side.side.GameEngine.paint(GameEngine.java:64) 
     at javax.swing.JComponent.paintChildren(Unknown Source) 
     at javax.swing.JComponent.paint(Unknown Source) 
     at javax.swing.JComponent.paintChildren(Unknown Source) 
     at javax.swing.JComponent.paint(Unknown Source) 
     at javax.swing.JLayeredPane.paint(Unknown Source) 
     at javax.swing.JComponent.paintChildren(Unknown Source) 
     at javax.swing.JComponent.paintToOffscreen(Unknown Source) 
     at javax.swing.RepaintManager$PaintManager.paintDoubleBuffered(Unknown Source) 
     at javax.swing.RepaintManager$PaintManager.paint(Unknown Source) 
     at javax.swing.RepaintManager.paint(Unknown Source) 
     at javax.swing.JComponent.paint(Unknown Source) 
     at java.awt.GraphicsCallback$PaintCallback.run(Unknown Source) 
     at sun.awt.SunGraphicsCallback.runOneComponent(Unknown Source) 
     at sun.awt.SunGraphicsCallback.runComponents(Unknown Source) 
     at java.awt.Container.paint(Unknown Source) 
     at java.awt.Window.paint(Unknown Source) 
     at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
     at javax.swing.RepaintManager.paintDirtyRegions(Unknown Source) 
     at javax.swing.RepaintManager.seqPaintDirtyRegions(Unknown Source) 
     at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(Unknown Source) 
     at java.awt.event.InvocationEvent.dispatch(Unknown Source) 
     at java.awt.EventQueue.dispatchEvent(Unknown Source) 
     at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) 
     at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) 
     at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) 
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
     at java.awt.EventDispatchThread.pumpEvents(Unknown Source) 
     at java.awt.EventDispatchThread.run(Unknown Source) 

ライン64：

if (globalmap[x][y] == '1') { g2d.fillRect(10*y, 10*x, 10,10); } 

Answer 1

あなたのglobalmap配列要素nullですが、あなたが投稿している内容に基づいて伝えるのは難しいです。この行はひどいことに注意してください：

if (globalmap[x][y] == '1'){g2d.fillRect(10*y, 10*x, 10,10);} 

あなたはデバッグ専用のためならば、いくつかの行にこれを広めるために必要があります。

if (globalmap[x][y] == '1') { 
    g2d.fillRect(10*y, 10*x, 10,10); 
}