Java - 找不到符號？

Question

我在這裏練習一點，但我無法弄清楚。我宣佈ArrayList ns但它無法找到： 錯誤：無法找到符號ns.Add（aa）; 爲什麼？當然，我根本沒有看到明顯的東西。

import javax.swing.*; 
import java.awt.*; 
import java.awt.image.*; 
import java.awt.event.*; 
import java.util.Random; 
import java.util.*; 
import java.io.*; 


public class Pixels6 extends JFrame 
{ 
static java.util.List ns = new ArrayList(); 


class PaintingComponent extends JPanel 
{ 
    public void paintComponent(Graphics g) 
    { 
     super.paintComponent(g); 
     setBackground(Color.black); 
    } 
} 

public static void main(String[] args) throws InterruptedException, IOException 

{ 
    try 
    { 
      fl = new FileInputStream("test_for_java2.s8"); 
      aa = fl.read(); 

    javax.swing.Timer swTimer = new javax.swing.Timer(10, new ActionListener() 
    { 
     public void actionPerformed(ActionEvent ae) 
     {    
      if (aa!=-1) 
      { 
       aa -= 128; 
       aa = -aa; 
       ns.Add(aa); 
       try 
        {aa=fl.read(); }  
       catch(IOException e) 
       { 
        System.out.println("Access denied: " + e); 
        System.out.println(e); 
       } 
      } 
      else try 
        {fl.close();} 
       catch(IOException e) 
       { 
        System.out.println("Access denied: " + e); 
        System.out.println(e); 
       } 
     } /// Action 

    }); /// Timer 
    swTimer.start(); 

    } //try 

    catch(IOException e) 
     { 
      System.out.println("Access denied: " + e); 
      System.out.println(e); 
     } 


    SwingUtilities.invokeLater(new Runnable() 
    { 
     public void run() 
     { 
      new Pixels6().setVisible(true); 
     } 
    }); 

} /// main 

} /// Pixels6 extends JFrame 

Answer 1

變化

ns.add(aa); //not ns.Add(aa); 

Java是大小寫敏感的語言