[問題] java.lang.NullPointerException

[qwe801031 (karoro)]

目前想做一個介面有兩個按鈕，一個是讀入HTML的東西，另一個是HTML讀入後丟到HASH裡

原本這兩個是分別兩隻程式

合到一起後製作介面

想說把讀入的資料都string到SS裡

然後HASH，ss裡的資料這樣

但出現Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException

原本分個的時候都可以執行

雖然分開時hash時是

 String Str = new String("Welcome to Tutorialspoint.com");
      System.out.println("Hashcode for Str :" + Str.hashCode() );

這樣而已


之後介面的程式碼如下


package com.manze.stu;

import java.awt.BorderLayout;
import java.awt.EventQueue;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.JButton;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.net.*;
import java.io.*;

public class Testface extends JFrame {


         String ss;
        private JPanel contentPane;



        /**
         * Launch the application.
         */
        public static void main(String[] args) {
                EventQueue.invokeLater(new Runnable() {
                        public void run() {
                                try {
                                        Testface frame = new Testface();
                                        frame.setVisible(true);
                                } catch (Exception e) {
                                        e.printStackTrace();
                                }
                        }
                });
        }



        /**
         * Create the frame.
         */
        public Testface() {
                setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                setBounds(100, 100, 450, 300);
                contentPane = new JPanel();
                contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
                setContentPane(contentPane);
                contentPane.setLayout(null);

                JButton btnHash = new JButton("read htm");
                btnHash.addActionListener(new ActionListener() {

                        public void actionPerformed(ActionEvent e) {


                                 try {
                                    File fileDir = new File("D:\\ea.htm");

                                    BufferedReader in = new BufferedReader(
                                            new InputStreamReader(
                                                    new FileInputStream(fileDir), "UTF8"));



                                    while ((ss = in.readLine()) != null) {
                                        System.out.println(ss);
                                    }

                                    in.close();
                                }catch (UnsupportedEncodingException e1){
                                    System.out.println(e1.getMessage());
                                }catch (IOException e1){
                                    System.out.println(e1.getMessage());
                                }catch (Exception e1){
                                    System.out.println(e1.getMessage());
                                }


                        }

                });
                btnHash.setBounds(10, 22, 123, 23);
                contentPane.add(btnHash);

                JButton btnReadHtml = new JButton("hash");
                btnReadHtml.addActionListener(new ActionListener() {
                        public void actionPerformed(ActionEvent e) {

                                 String Str = new String(ss);


                              System.out.println("Hashcode for Str :" + Str.hashCode() );



                        }
                });
                btnReadHtml.setBounds(10, 88, 123, 23);
                contentPane.add(btnReadHtml);

                JButton btnNewButton = new JButton("Signature");
                btnNewButton.setBounds(10, 181, 123, 23);
                contentPane.add(btnNewButton);

        }
}


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