时间紧 今天就需 大姥求解

package ui;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

import Inteface.WebCache;

public class MainFrame extends JFrame implements Inteface.MainFrame {
// 图形界面
private JButton Buttonstart;
private JButton Buttonstop;
private JButton ButtonsetDir;
private JButton Buttonsetport;
private JTextField Textport;
private JTextArea TextMessage;
private JPanel right;
private JPanel bottom;
// Web Cache代理服务器
private WebCache webcache;
private String DIR;
private int PORT;

public MainFrame() {
    super("Web缓存服务器");
    init();
}

private void init() {
    Config();
    addCon();
    showFrame();

}

private void showFrame() {
    this.pack();
    this.setVisible(true);
    this.setLocationRelativeTo(null);
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
}

private void addCon() {
    bottom.add(Buttonstart);
    bottom.add(Buttonstop);
    bottom.add(Buttonsetport);
    bottom.add(ButtonsetDir);

    right.add(Textport);
    right.add(Buttonsetport);
    bottom.add(right);

    this.add(new JScrollPane(TextMessage));
    this.add(bottom, BorderLayout.SOUTH);
}

private void Config() {
    Buttonstart = new JButton("启动");
    Buttonstop = new JButton("停止");
    Buttonsetport = new JButton("设置端口");
    ButtonsetDir = new JButton("设置缓存目录");
    Textport = new JTextField(4);
    TextMessage = new JTextArea(10, 20);
    right = new JPanel(new FlowLayout());
    bottom = new JPanel();
    ButtonsetDir.addActionListener(e -> {
        JFileChooser jchose = new JFileChooser();
        jchose.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
        int returnValue = jchose.showOpenDialog(this);
        if (returnValue == JFileChooser.APPROVE_OPTION) {
            File file = jchose.getSelectedFile();
            DIR = file.getPath();
            webcache.setdir(DIR);
        }
    });

    Buttonstop.setEnabled(false);

    Buttonsetport.addActionListener(e -> {
        setport();
    });
    Buttonstop.addActionListener(e -> {
        Buttonstart.setEnabled(true);
        Buttonstop.setEnabled(false);
        Buttonsetport.setEnabled(true);
        Textport.setEnabled(true);
    });
    start();
    stop();
}

@Override
public void start() {
    // TODO Auto-generated method stub
    Buttonstart.addActionListener(e -> {
        if (DIR == null)
            JOptionPane.showMessageDialog(this, "请选择缓存目录");
        else if (PORT == 0)
            JOptionPane.showMessageDialog(this, "请设置端口号");
        else {
            String str = webcache.startServer();
            if (str.equals("true")) {
                Messageappend("启动成功");
                Buttonstart.setEnabled(false);
                Buttonstop.setEnabled(true);
                Buttonsetport.setEnabled(false);
                Textport.setEnabled(false);
            } else {
                Buttonstart.setEnabled(true);
                Buttonstop.setEnabled(false);
                Buttonsetport.setEnabled(true);
                Textport.setEnabled(true);
                Messageappend(str);
            }
        }

    });
}

public void Messageappend(String str) {
    if (str == null)
        TextMessage.append("\n");

    TextMessage.append(str + "\n");
}

@Override
public void stop() {
    // TODO Auto-generated method stub
    Buttonstop.addActionListener(e -> {
        webcache.stopServer();
    });
}

@Override
public void setport() {
    // TODO Auto-generated method stub
    PORT = Integer.parseInt((Textport.getText().trim()));
    System.out.println(PORT);
    webcache.setport(PORT);
}

@Override
public void setWebCache(Inteface.WebCache webcache) {
    // TODO Auto-generated method stub

}

}

错误
8090
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException: Cannot invoke "Inteface.WebCache.setport(int)" because "this.webcache" is null
at ui.MainFrame.setport(MainFrame.java:149)
at ui.MainFrame.lambda$1(MainFrame.java:89)

放下手上所有的事情，以宇宙速度解决了问题，修改后的完整代码如下：

package ui;

import java.awt.BorderLayout;
import java.awt.FlowLayout;
import java.io.File;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

import Inteface.WebCache;

public class MainFrame extends JFrame implements Inteface.MainFrame {
    // 图形界面
    private JButton Buttonstart;
    private JButton Buttonstop;
    private JButton ButtonsetDir;
    private JButton Buttonsetport;
    private JTextField Textport;
    private JTextArea TextMessage;
    private JPanel right;
    private JPanel bottom;
    // Web Cache代理服务器
    private WebCache webcache;
    private String DIR;
    private int PORT;

    public MainFrame() {
        super("Web缓存服务器");
        init();
    }

    private void init() {
        Config();
        addCon();
        showFrame();

    }

    private void showFrame() {
        this.pack();
        this.setVisible(true);
        this.setLocationRelativeTo(null);
        this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    private void addCon() {
        bottom.add(Buttonstart);
        bottom.add(Buttonstop);
        bottom.add(Buttonsetport);
        bottom.add(ButtonsetDir);

        right.add(Textport);
        right.add(Buttonsetport);
        bottom.add(right);

        this.add(new JScrollPane(TextMessage));
        this.add(bottom, BorderLayout.SOUTH);
    }

    private void Config() {
        Buttonstart = new JButton("启动");
        Buttonstop = new JButton("停止");
        Buttonsetport = new JButton("设置端口");
        ButtonsetDir = new JButton("设置缓存目录");
        Textport = new JTextField(4);
        TextMessage = new JTextArea(10, 20);
        right = new JPanel(new FlowLayout());
        bottom = new JPanel();
        ButtonsetDir.addActionListener(e -> {
            JFileChooser jchose = new JFileChooser();
            jchose.setFileSelectionMode(JFileChooser.DIRECTORIES_ONLY);
            int returnValue = jchose.showOpenDialog(this);
            if (returnValue == JFileChooser.APPROVE_OPTION) {
                File file = jchose.getSelectedFile();
                DIR = file.getPath();
                webcache.setdir(DIR);
            }
        });

        Buttonstop.setEnabled(false);

        Buttonsetport.addActionListener(e -> {
            setport();
        });
        Buttonstop.addActionListener(e -> {
            Buttonstart.setEnabled(true);
            Buttonstop.setEnabled(false);
            Buttonsetport.setEnabled(true);
            Textport.setEnabled(true);
        });
        start();
        stop();
    }

    @Override
    public void start() {
        // TODO Auto-generated method stub
        Buttonstart.addActionListener(e -> {
            if (DIR == null)
                JOptionPane.showMessageDialog(this, "请选择缓存目录");
            else if (PORT == 0)
                JOptionPane.showMessageDialog(this, "请设置端口号");
            else {
                String str = webcache.startServer();
                if (str.equals("true")) {
                    Messageappend("启动成功");
                    Buttonstart.setEnabled(false);
                    Buttonstop.setEnabled(true);
                    Buttonsetport.setEnabled(false);
                    Textport.setEnabled(false);
                } else {
                    Buttonstart.setEnabled(true);
                    Buttonstop.setEnabled(false);
                    Buttonsetport.setEnabled(true);
                    Textport.setEnabled(true);
                    Messageappend(str);
                }
            }

        });
    }

    public void Messageappend(String str) {
        if (str == null)
            TextMessage.append("\n");

        TextMessage.append(str + "\n");
    }

    @Override
    public void stop() {
        // TODO Auto-generated method stub
        Buttonstop.addActionListener(e -> {
            webcache.stopServer();
        });
    }

    @Override
    public void setport() {
        // TODO Auto-generated method stub
        PORT = Integer.parseInt((Textport.getText().trim()));
        System.out.println(PORT);
        webcache.setport(PORT);
    }

    @Override
    public void setWebCache(Inteface.WebCache webcache) {
        this.webcache = webcache;
        this.webcache.setFrame(this);
    }

}

如有帮助，请采纳，十分感谢！

Cannot invoke "Inteface.WebCache.setport(int)" because "this.webcache" is null

this.webcache这个对象为空