1、编写主方法实现启动类

import javax.swing.*;
 //主启动类
 public class StartGame {
 public static void main(String[] args) {
 JFrame jFrame = new JFrame("贪吃蛇小游戏");
 jFrame.setBounds(10,10,900,720);
 jFrame.setResizable(false); //设置窗口大小不可变
 jFrame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
 //面板
 jFrame.add(new GamePanel());
 jFrame.setVisible(true);
 }
}

2、准备好素材图片，编写数据类

import javax.swing.*;
import java.net.URL;


public class Data {
 //头部图片
 public static URL headerURL = Data.class.getResource("statics/header.png");
 public static ImageIcon header = new ImageIcon(headerURL);
 //头部上下左右
 public static URL upURL = Data.class.getResource("statics/up.png");
 public static URL downURL = Data.class.getResource("statics/down.png");
 public static URL leftURL = Data.class.getResource("statics/left.png");
 public static URL rightURL = Data.class.getResource("statics/right.png");
 public static ImageIcon up = new ImageIcon(upURL);
 public static ImageIcon down = new ImageIcon(downURL);
 public static ImageIcon left = new ImageIcon(leftURL);
 public static ImageIcon right = new ImageIcon(rightURL);
 //身体
 public static URL bodyURL = Data.class.getResource("statics/body.png");
 public static ImageIcon body = new ImageIcon(bodyURL);
 //食物
 public static URL foodURL = Data.class.getResource("statics/food.png");
 public static ImageIcon food = new ImageIcon(foodURL);

}

3、代码主体部分：在panel面板上实现游戏初始化，键盘和事件的监听等功能

package com.abc.snake;

import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;
import java.util.Random;

//游戏的面板
public class GamePanel extends JPanel implements KeyListener, ActionListener {
 //定义蛇的数据结构
 int length; //蛇的长度
 int[] snakeX = new int[600]; //蛇的x坐标 25*25
 int[] snakeY = new int[500]; //蛇的y坐标 25*25
 String fx;
 //食物
 int foodx;
 int foody;
 Random random = new Random();
 int score; //游戏分数
 //游戏当前的状态
 boolean isStart = false;
 boolean isFail = false; 
 //定时器
 Timer timer = new Timer(100,this);//100毫秒刷新一次
 //构造方法
 public GamePanel() {
 init();//初始化
 this.setFocusable(true); //获得焦点事件
 this.addKeyListener(this); //获得键盘监听事件
 timer.start(); //游戏一开始 定时器就启动
 }

 //初始化方法
 public void init(){
 length = 3;
 //初始化开始的蛇，给蛇定位
 snakeX[0] = 100;snakeY[0] = 100;
 snakeX[1] = 75;snakeY[1] = 100;
 snakeX[2] = 50;snakeY[2] = 100;
 fx = "R";  //初始方向向右
 //初始化食物数据
 foodx = 25 + 25*random.nextInt(34);
 foody = 75 + 25*random.nextInt(24);
 //初始化游戏分数
 score = 0;
 }


 //绘制面板
 @Override
 protected void paintComponent(Graphics g) {
 super.paintComponent(g);//清屏
 this.setBackground(Color.white);//设置面板背景色
 Data.header.paintIcon(this,g,25,11);//头部
 g.fillRect(25,75,850,600);//默认的黑色游戏区域

 //绘制小蛇
 if (fx.equals("R")){
  Data.right.paintIcon(this,g,snakeX[0],snakeY[0]); //蛇头初始化向右
 }else if (fx.equals("L")){
  Data.left.paintIcon(this,g,snakeX[0],snakeY[0]); //蛇头初始化向左
 }else if (fx.equals("U")){
  Data.up.paintIcon(this,g,snakeX[0],snakeY[0]); //蛇头初始化向上
 }else if (fx.equals("D")){
  Data.down.paintIcon(this,g,snakeX[0],snakeY[0]); //蛇头初始化向下
 }
 for (int i = 1; i < length; i++) {
  Data.body.paintIcon(this,g,snakeX[i],snakeY[i]);
 }

 //食物
 Data.food.paintIcon(this,g,foodx,foody);
 //积分
 g.setColor(Color.white);
 g.setFont(new Font("微软雅黑",Font.BOLD,18));
 g.drawString("长度 "+length,750,35);
 g.drawString("分数 "+score,750,50);
 //游戏状态
 if (isStart == false){
  g.setColor(Color.white);
  g.setFont(new Font("微软雅黑",Font.BOLD,40));//设置字体
  g.drawString("按下空格开始游戏",300,300);
 }
 //失败判断
 if (isFail){
  g.setColor(Color.red);
  g.setFont(new Font("微软雅黑",Font.BOLD,40));//设置字体
  g.drawString("游戏失败，按下空格重新开始",300,300);
 }
 }
 
 //键盘监听事件
 @Override
 public void keyPressed(KeyEvent e) {
 int keyCode = e.getKeyCode(); //获取按键
 if (keyCode == KeyEvent.VK_SPACE){
  if (isFail){
  //重新开始
  isFail=false;
  init();
  }else {
  isStart =! isStart; 
  }
  repaint();
 }

 //键盘控制小蛇移动
 if (keyCode==KeyEvent.VK_UP){
  fx="U";
 }else if (keyCode==KeyEvent.VK_DOWN){
  fx="D";
 }else if (keyCode==KeyEvent.VK_LEFT){
  fx="L";
 }else if (keyCode==KeyEvent.VK_RIGHT){
  fx="R";
 }
 }
 //事件监听
 @Override
 public void actionPerformed(ActionEvent e) {
 if (isStart && isFail ==false){//如果游戏是开始状态，就让小蛇动起来
  //移动
  for (int i = length-1; i > 0 ; i--) {
  snakeX[i] = snakeX[i-1];
  snakeY[i] = snakeY[i-1];
  }
  //走向
  if (fx.equals("R")){
  snakeX[0] = snakeX[0]+25;
  //边界判断
  if (snakeX[0]>850){
   snakeX[0]=25;
  }
  }else if (fx.equals("L")){
  snakeX[0] = snakeX[0]-25;
  if (snakeX[0]<25){
   snakeX[0]=850;
  }
  }else if (fx.equals("U")){
  snakeY[0] = snakeY[0]-25;
  if (snakeY[0]<75){
   snakeY[0]=650;
  }
  }else if (fx.equals("D")){
  snakeY[0] = snakeY[0]+25;
  if (snakeY[0]>650){
   snakeY[0]=75;
  }
  }
  //吃食物
  if (snakeX[0] == foodx && snakeY[0] == foody){
  length++;
  score = score + 10;
  //再次随机食物
  foodx = 25 + 25*random.nextInt(34);
  foody = 75 + 25*random.nextInt(24);
  }
  //失败判定,撞到自己
  for (int i = 1; i < length; i++) {
  if (snakeX[0]==snakeX[i] && snakeY[0]==snakeY[i]){
   isFail=true;
  }
  }
  repaint();
 }
 timer.start();
 }
 @Override
 public void keyTyped(KeyEvent e) {
 }
 @Override
 public void keyReleased(KeyEvent e) {
 }
}

4、代码运行效果图

初始化界面：

游戏中界面：

游戏结束界面：