Question

我的程序有问题，它是流程完成但是运行时异常java.lang.NullPointerException。有人可以帮帮我吗？到目前为止，这是我的代码。

  import javax.swing.*;
import java.lang.Character;
import java.io.*;
public class CoproHW
{
    public static String c;
    public static int NOc;
    public static String vince;
    public static void main(String args [])throws IOException
    {

        String vince = JOptionPane.showInputDialog("Enter Your File path :");
         c = JOptionPane.showInputDialog("Enter a character");

        briefer();
    }
    public static void briefer()
    {

        for(int v = 1; v<c.length(); v++)
        {
            char x = c.charAt(v);
            if(Character.isSpaceChar(x))
            {
                NOc++;
            }


            char z = c.charAt(v);
            if(Character.isLetter(z))
            {
                NOc++;
            }
        }

        panty();
    }
    public static void panty()
    {
        File file = new File(vince);

        if(!file.exists())
        {
            JOptionPane.showMessageDialog(null,"Wrong file path !");
        }
        else
        {
            JOptionPane.showMessageDialog(null, "The Number of Characters in "+ c +" is "+ NOc);

            try
            {
                RandomAccessFile gui = new RandomAccessFile(file," ");

                gui.writeBytes("The number of Characters in "+ c + " is " +NOc);
                gui.close();
            }

            catch(IOException m)
            {
                System.out.print(m.getMessage());
                System.exit(0);
            }
        }
    }
}

Answer 1

因为您没有为全局vince变量指定值。而是将期望值分配给局部变量：

String vince = JOptionPane.showInputDialog("Enter Your File path :");

将代码修改为：

vince = JOptionPane.showInputDialog("Enter Your File path :");

然后它会起作用。

Answer 2

删除主要方法的String。

vince = JOptionPane.showInputDialog("Enter Your File path :");

这是您已声明的全局变量。

在java.lang.NullPointerExceptions中出错

2 个答案: