复习Java第二个项目仿QQ聊天系统 01（界面部分） &Java面试题Redis的过期策略和内存淘汰策略&生活【记录一个咸鱼大学生三个月的奋进生活】023

本文链接：https://blog.youkuaiyun.com/coiokok/article/details/119245060

本文记录了一位咸鱼大学生在复习Java时制作仿QQ聊天系统的过程，包括设置背景的ImgPanel类，登录界面LoginFrame、注册界面RegisterFrame、好友列表界面MainFrame、发送及接收信息界面SendFrame和ReceiveFrame。同时，探讨了Redis的过期策略和内存淘汰策略，是Java Swing应用与后端知识结合的实践案例。

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复习Java（仿QQ聊天系统01界面部分）

在我们学完多线程、I/O、网络编程等知识后应该做个项目来实践一下之前学的知识，我能想到的就是做一个简易的仿照QQ的聊天系统，我们可以通过 多线程实现一个又一个用户的登录，网络传输和I/O来配合实现发送和接收消息，Javaswing实现系统的可视化 等。
该项目分为client客户端代码和server服务器端代码并配合MVC分层设计模式，今天先从ui界面层开始一步一步复习。

每个代码的意思我也在备注里标注的很清楚了，再有不明白的或者改进意见的大家可以在评论区指出！

设置背景（ImgPanel）类

package com.test;

// 设置背景图片的panel类，比第一次项目改进了一下，这次重写了构造方法，可以直接在实例化时传入图片路径就可以把图片设置为panel背景

import java.awt.Graphics;
import java.io.File;

import javax.swing.ImageIcon;
import javax.swing.JPanel;


public class ImgPanel extends JPanel {
	private ImageIcon img = null;
	
	// 获得当前项目的绝对路径
	public String getSystempath() {
        File f = new File("");
        return f.getAbsolutePath();
    }
	
	
	public ImgPanel() {
		// TODO Auto-generated constructor stub
	}
	// 重写构造方法传入图片路径再用ImageIcon实例化，然后再通过paintComponent实例化图片背景
	public ImgPanel(String imgPath) {
		this.img = new ImageIcon(this.getSystempath() + imgPath );
	}
	

	@Override
	protected void paintComponent(Graphics g) {
		// 画笔设置图片背景方法
		g.drawImage(this.img.getImage(), 0, 0, this);
	}
}

登录界面（LoginFrame）类

package com.test;

// 用户进行登录的页面

import java.awt.BorderLayout;
import java.awt.Font;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;


public class LoginFrame extends JFrame{
	
	private JPanel bodyPanel;                     // 所有界面panel，一个大body和中间的登录框centerPanel以及底部的按钮bottomPanel
	private JPanel centerPanel;
	private JPanel bottomPanel;
	
	private JLabel accountLabel;                  // 用户名和密码的输入panel
	private JTextField accountTextField;
	private JLabel passowrdLabel;
    private JPasswordField passwordField;
    
    private JButton loginButton;                  // 登录和注册按钮
    private JButton registerButton;
    
    // 中间的操作panel
    private void initCenter() {
    	this.centerPanel = new ImgPanel("./img/login.png");       // 实例化ImgPanel专门设背景的对象将登录页面的背景图片传入
    	
    	this.accountLabel = new JLabel("用 户 名：");
        this.accountTextField = new JTextField(16);
		this.accountLabel.setFont(new Font("微软雅黑", Font.BOLD, 17));        // setFont(new Font("字体", Font.样式, 字体大小))    设置字体样式的方法
        this.passowrdLabel = new JLabel("密     码：");
        this.passwordField = new JPasswordField(16);
		this.passowrdLabel.setFont(new Font("微软雅黑", Font.BOLD, 18));        // setFont(new Font("字体", Font.样式, 字体大小))    设置字体样式的方法
        
        // 设置box布局管理器
        Box box0 = Box.createVerticalBox();
        Box box1 = Box.createHorizontalBox();
        Box box2 = Box.createHorizontalBox();
        
        box1.add(accountLabel);
        box1.add(accountTextField);
        
        box2.add(passowrdLabel);
        box2.add(passwordField);
        
        box0.add(Box.createVerticalStrut(90));
        box0.add(box1);
        box0.add(Box.createVerticalStrut(20));
        box0.add(box2);
        this.centerPanel.add(box0);
    }
    
    // 底部的按钮panel
    private void initBottom() {
    	this.bottomPanel = new JPanel();
        this.loginButton = new JButton("登 录");
        this.bottomPanel.add(this.loginButton);
        
        this.registerButton = new JButton("注 册");
        this.bottomPanel.add(this.registerButton); 
    }
    
    // 窗体代码
    private void init() {
    	this.bodyPanel = (JPanel)this.getContentPane();
    	this.bodyPanel.setLayout(new BorderLayout());
    	
    	this.initCenter();
    	this.bodyPanel.add(this.centerPanel, BorderLayout.CENTER);
    	
    	this.initBottom();
    	this.bodyPanel.add(this.bottomPanel, BorderLayout.SOUTH);
    	
    	this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setTitle("QQ登录页面");
    }
    
    // 重写构造方法
    public LoginFrame() {
    	this.init();
	}
   
    // 主方法运行main方法
	public static void main(String[] args) {
		LoginFrame loginFrame1 = new LoginFrame();
		loginFrame1.setBounds(680, 340, 500, 320);
		loginFrame1.setVisible(true);
	}
}

登录界面的效果：

注册界面（RegisterFrame）类

package com.test;

// 用户进行注册的页面
// 1.0是静态的注册页面代码

import java.awt.BorderLayout;
import java.awt.Dimension;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;

public class RegisterFrame extends JFrame {
	
		
	private JPanel bodyPanel = null;
	private JPanel centerPanel = null;
    private JPanel bottomPanel = null;
    
    private JLabel accountLabel = null;
    private JLabel nameLabel = null;
    private JLabel passwordLabel = null;
    private JLabel repasswordLabel = null;
    private JLabel imgLabel = null;
    
    private JTextField accountTextField = null;
    private JTextField nameTextField = null;
    private JPasswordField passwordField = null;
    private JPasswordField repasswordField = null;
    private JComboBox imgComboBox = null;
    
    private JButton registerButton = null;
    private JButton cancelButton = null;
 
    
    // 中间输入信息界面的代码
    private void initCenter() {
    	// 通过ImgPanel的构造方法实例化panel背景
    	this.centerPanel = new ImgPanel("./img/register.png");
    	
    	this.accountLabel = new JLabel("用  户  名 ：", JLabel.RIGHT);
		this.accountLabel.setPreferredSize(new Dimension(70, 24));       // .setPreferredSize(new Dimension(宽, 高))    设置panel大小方法但是会随着界面大小变化而变化
    	this.nameLabel = new JLabel("昵         称：", JLabel.RIGHT);
		this.nameLabel.setPreferredSize(new Dimension(70, 24));
		this.passwordLabel = new JLabel("密         码：", JLabel.RIGHT);
		this.passwordLabel.setPreferredSize(new Dimension(70, 24));
		this.repasswordLabel = new JLabel("确认密码：", JLabel.RIGHT);
		this.repasswordLabel.setPreferredSize(new Dimension(70, 24));
		this.imgLabel = new JLabel("选择头像：", JLabel.RIGHT);
		this.imgLabel.setPreferredSize(new Dimension(70, 24));
		
		this.accountTextField = new JTextField();
	    this.accountTextField.setPreferredSize(new Dimension(160, 24));
		this.nameTextField = new JTextField();
		this.nameTextField.setPreferredSize(new Dimension(160, 24));
		this.passwordField = new JPasswordField();
		this.passwordField.setPreferredSize(new Dimension(160, 24));
		this.repasswordField = new JPasswordField();
		this.repasswordField.setPreferredSize(new Dimension(160, 24));
		this.imgComboBox = new JComboBox();
		
		// Box布局管理器，需要五个横着panel时需要声明一个大的竖着的box包裹住五个横着的box
		Box box0 = Box.createVerticalBox();              // .createVerticalBox()创建竖着的box方法
		Box box1 = Box.createHorizontalBox();            // .createHorizontalBox()创建横着的box方法
		Box box2 = Box.createHorizontalBox();
		Box box3 = Box.createHorizontalBox();
		Box box4 = Box.createHorizontalBox();
		Box box5 = Box.createHorizontalBox();
		
		box1.add(this.accountLabel);
		box1.add(this.accountTextField);
		
		box2.add(this.nameLabel);
		box2.add(this.nameTextField);
		
		box3.add(this.passwordLabel);
		box3.add(this.passwordField);
		
		box4.add(this.repasswordLabel);
		box4.add(this.repasswordField);
		
		box5.add(this.imgLabel);
		box5.add(this.imgComboBox);
		
		box0.add(Box.createVerticalStrut(90));            // .createVerticalStrut(间距)设置每个box之间间距的方法
		box0.add(box1);
		box0.add(Box.createVerticalStrut(10));
		box0.add(box2);
		box0.add(Box.createVerticalStrut(10));
		box0.add(box3);
		box0.add(Box.createVerticalStrut(10));
		box0.add(box4);
		box0.add(Box.createVerticalStrut(10));
		box0.add(box5);
		
		this.centerPanel.add(box0);
    }
    
    // 下方按钮panel的代码
    private void initBottom() {
    	this.bottomPanel = new JPanel();
    	
    	this.registerButton = new JButton("注 册");
    	this.cancelButton = new JButton("重 置");
    	
    	this.bottomPanel.add(this.registerButton);
    	this.bottomPanel.add(this.cancelButton);
    }
    
    // 生成窗体的方法
    private void init() {
    	this.bodyPanel = (JPanel)this.getContentPane();
    	this.bodyPanel.setLayout(new BorderLayout());
    	
    	this.initCenter();
    	this.bodyPanel.add(this.centerPanel, BorderLayout.CENTER);
    
    	this.initBottom();
    	this.bodyPanel.add(this.bottomPanel, BorderLayout.SOUTH);
    	
    	this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    	this.setTitle("QQ注册页面");
    }
    
    // 重写构造方法，实例化时生成注册窗体并与服务器进行传输通讯连接
    public RegisterFrame() {
		this.init();	
	}
    
	public static void main(String[] args) {
		RegisterFrame registerFrame = new RegisterFrame();
		registerFrame.setBounds(700, 320, 512, 390);
		registerFrame.setVisible(true);
	}
}

注册界面的效果：

好友列表界面（MainFrame）类

package com.test;

// 好友列表页面

import java.awt.BorderLayout;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;

public class MainFrame extends JFrame {
	
	private JLabel userLabel = null;                  // 该用户名的顶部panel
	
	private JPanel bodyPanel = null;
	
	// 重写构造方法
	public MainFrame() {
		// TODO Auto-generated constructor stub
		this.init();
	}
	
	// init主页面方法
	private void init() {
		this.bodyPanel = (JPanel)this.getContentPane();
		this.bodyPanel.setLayout(new BorderLayout());
		
		this.userLabel = new JLabel("test的好友列表"); 
		this.bodyPanel.add(this.userLabel, BorderLayout.NORTH);
		
		this.setBounds(1625, 0, 300, 800);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setTitle("test的好友列表");
	}
	
	public static void main(String[] args) {
		MainFrame MainFrame = new MainFrame();
		MainFrame.setBounds(1625, 0, 300, 800);
		MainFrame.setVisible(true);
	}
}

好友列表界面的效果：

发送信息界面（SendFrame）类

package com.test;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class SendFrame extends JFrame {
	
	private JPanel topPanel;
    private JPanel bottomPanel;
    
    private JLabel receiverLabel = null;
   	private JTextField receiverField = null;
   	private JLabel sendercontentLabel = null;
    private JTextArea sendArea;
    
    private JButton sendButton;
    private JButton closeButton;
    
    private void init() {
    	JPanel bodyPanel = (JPanel)this.getContentPane();
		bodyPanel.setLayout(new BorderLayout());
		
		this.topPanel = new JPanel();
		this.bottomPanel = new JPanel();
		bodyPanel.add(this.topPanel, BorderLayout.CENTER);
		bodyPanel.add(this.bottomPanel, BorderLayout.SOUTH);
		
		this.receiverLabel = new JLabel("接收者：");
        this.receiverField = new JTextField();
        this.receiverField.setPreferredSize(new Dimension(400, 25));
        this.receiverField.setEditable(false);
        this.receiverField.setText("test的接收者");
        
        this.sendercontentLabel = new JLabel("发送内容：");
        this.sendArea = new JTextArea();
        this.sendArea.setPreferredSize(new Dimension(400, 130));
        JScrollPane sendScrollPane = new JScrollPane(this.sendArea);
        
        Box box = Box.createVerticalBox();
        
        Box box1 = Box.createHorizontalBox();
        Box box2 = Box.createHorizontalBox();
        
        box1.add(this.receiverLabel);
        box1.add(this.receiverField);
        
        box2.add(this.sendercontentLabel);
        box2.add(sendScrollPane);
        
        box.add(Box.createVerticalStrut(10));
        box.add(box1);
        box.add(Box.createVerticalStrut(10)); 
        box.add(box2);
        
        this.topPanel.add(box);
        
        this.bottomPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 50, 10));
        this.sendButton = new JButton("发送");
        this.closeButton = new JButton("关闭");
        this.bottomPanel.add(this.sendButton);
        this.bottomPanel.add(this.closeButton);
        
        this.setTitle("test的发送框");
        this.setBounds(600, 370, 500, 280);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    public SendFrame() {
		// TODO Auto-generated constructor stub
    	this.init();
	}

    public static void main(String[] args) {
    	SendFrame SendFrame = new SendFrame();
    	SendFrame.setBounds(700, 360, 500, 280);
    	SendFrame.setVisible(true);
	}
}

发送信息界面的效果：

接收信息界面（ReceiveFrame）类

package com.test;

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.FlowLayout;

import javax.swing.Box;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class ReceiveFrame extends JFrame {
	private String message = null;
	
	private JPanel topPanel;
    private JPanel bottomPanel;
    
    private JLabel fromLabel = null;
   	private JTextField fromField = null;
   	private JLabel contentLabel = null;
    private JTextArea contentArea;
    
    private JButton repeatButton;
    private JButton closeButton;
    
    private void init() {
    	JPanel bodyPanel = (JPanel)this.getContentPane();
		bodyPanel.setLayout(new BorderLayout());
		
		this.topPanel = new JPanel();
		this.bottomPanel = new JPanel();
		bodyPanel.add(this.topPanel, BorderLayout.CENTER);
		bodyPanel.add(this.bottomPanel, BorderLayout.SOUTH);
		
		this.fromLabel = new JLabel("来自于：");
        this.fromField = new JTextField();
        this.fromField.setPreferredSize(new Dimension(400, 25));
        this.fromField.setEditable(false);
        this.fromField.setText("test");
        
        this.contentLabel = new JLabel("接收内容：");
        this.contentArea = new JTextArea();
        this.contentArea.setPreferredSize(new Dimension(400, 130));
        this.contentArea.setText(this.message);
        this.contentArea.setEditable(false);
        JScrollPane contentScrollPane = new JScrollPane(this.contentArea);
        
        Box box = Box.createVerticalBox();
        
        Box box1 = Box.createHorizontalBox();
        Box box2 = Box.createHorizontalBox();
        
        box1.add(this.fromLabel);
        box1.add(this.fromField);
        
        box2.add(this.contentLabel);
        box2.add(contentScrollPane);
        
        box.add(Box.createVerticalStrut(10));
        box.add(box1);
        box.add(Box.createVerticalStrut(10)); 
        box.add(box2);
        
        this.topPanel.add(box);
        
        this.bottomPanel.setLayout(new FlowLayout(FlowLayout.CENTER, 50, 10));
        this.repeatButton = new JButton("回复");
        this.closeButton = new JButton("关闭");
        this.bottomPanel.add(this.repeatButton);
        this.bottomPanel.add(this.closeButton);
        
        this.setTitle("test的接收框");
        this.setBounds(700, 360, 500, 280);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    }
    
    public ReceiveFrame() {
		// TODO Auto-generated constructor stub
    	this.init();
	}

    public static void main(String[] args) {
    	ReceiveFrame ReceiveFrame = new ReceiveFrame();
    	ReceiveFrame.setBounds(700, 360, 500, 280);
    	ReceiveFrame.setVisible(true);
	}
}