本篇是根据视频学习完成的，视频和静态资源在最末尾。
所以我就直接放代码了，详细过程看视频。
项目结构

Data.java

package snake;
import java.net.*;
import javax.swing.*;

//存放外部数据
public class Data {
	//头部的图片 URL：定位图片的地址 ImageIcon：图片
	public static URL headerURL = Data.class.getResource("/statics/header.png");
	public static ImageIcon header = new ImageIcon(headerURL);	
	
	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);
    
    public static URL bodyURL = Data.class.getResource("/statics/body.png");
    public static ImageIcon body = new ImageIcon(bodyURL);
    public static URL foodURL = Data.class.getResource("/statics/food.png");
    public static ImageIcon food = new ImageIcon(foodURL);

	
}

GamePanel.java

package 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;
public class GamePanel extends JPanel implements KeyListener, ActionListener{
	
	int lenth;//长度
	int[] snakeX = new int[600];
	int[] snakeY = new int[500];
	String fx;//RLUD左右上下
	Boolean isStart = false;//游戏开始没有
	Timer timer = new Timer(100,this);
	
	//定义一个食物
	int foodx;
	int foody;
	Random random = new Random();
	//死亡判断
	boolean isFail = false;
	//积分系统
	int score;
	//构造器
	public GamePanel() {
		init();
		//获取键盘的监听事件
		this.setFocusable(true);
		this.addKeyListener(this);
		timer.start();//让时间动起来
	}
	//初始化
	public void init() {
		lenth = 3;
		snakeX[0] =100;snakeY[0] = 100;
		snakeX[1] =75;snakeY[1] = 100;
		snakeX[2] =50;snakeY[2] = 100;
		fx = "R";
		
		foodx = 25+25*random.nextInt(34);
		foody = 75+25*random.nextInt(24);
		
		score = 0;
	}
	//画板 ：画界面，画蛇
	@Override
	protected void paintComponent(Graphics g)
	{
		super.paintComponent(g);//清屏
		this.setBackground(Color.WHITE);//背景颜色
		//绘制头部的广告栏
		Data.header.paintIcon(this, g, 25, 11);
		
		//绘制游戏区域
		g.fillRect(25, 75, 850, 600);
		
		//画蛇
		if(fx.equals("R"))
		{
			Data.right.paintIcon(this,g, snakeX[0], snakeY[0]);
		}
		else if(fx.equals("L"))
		{
			Data.left.paintIcon(this,g, snakeX[0], snakeY[0]);
		}
		else if(fx.equals("U"))
		{
			Data.up.paintIcon(this,g, snakeX[0], snakeY[0]);
		}
		else if(fx.equals("D"))
		{
			Data.down.paintIcon(this,g, snakeX[0], snakeY[0]);
		}
		
		
		for(int i=1;i<lenth;i++)
		{
			Data.body.paintIcon(this,g, snakeX[i], snakeY[i]);//蛇的身体长度通过lenth控制
		}
		//画积分
		g.setColor(Color.WHITE);
		g.setFont(new Font("微软雅黑",Font.BOLD,18));
		g.drawString("长度："+lenth, 750, 35);
		g.drawString("分数："+score, 750, 50);
		//画食物
		Data.food.paintIcon(this, g, foodx, foody);
		
		//游戏提示，是否开始
		if(isStart == false)
		{
			//画一个文字
			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);
		}
		//失败提醒
		if(isFail)
		{
			//画一个文字
			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,按下空格重新开始游戏", 200, 300);
		}
	}
	//接受键盘的输入:监听
	@Override
	public void keyTyped(KeyEvent e) {
		// TODO Auto-generated method stub
		//键盘按下，弹起
	}
	@Override
	public void keyPressed(KeyEvent e) {
		// TODO Auto-generated method stub
		//键盘按下，未释放
		//获取按下的键盘是哪个键
		int keyCode = e.getKeyCode();
		if(keyCode == KeyEvent.VK_SPACE)
		{
			if(isFail)//失败，游戏再来一次
			{
				isFail = false;
				init();//初始化游戏
			}
			else//暂停游戏
			{
				isStart = !isStart;
			}
			repaint();//刷新界面
		}
		//键盘控制走向
		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";
        }
	}
	@Override
	public void keyReleased(KeyEvent e) {
		// TODO Auto-generated method stub
		//释放某个键
	}
	//定时器：监听事件，帧
	@Override
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		//如果游戏处于开始转态，并且游戏没有结束
		if(isStart && isFail==false)
		{
			for(int i=lenth-1;i>0;i--)//除了脑袋身体都往前移动
			{
				snakeX[i] = snakeX[i-1];
				snakeY[i] = snakeY[i-1];
			}
			//通过控制方向让头部移动
			if(fx.equals("R"))
			{
                snakeX[0]=snakeX[0]+25;
                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; }
            }
			//如果小蛇的头和food坐标重合
			if(snakeX[0] == foodx && snakeY[0]==foody)
			{
				lenth++;
				score += 10;
				//重新生成food
				foodx = 25+25*random.nextInt(34);
				foody = 75+25*random.nextInt(24);
			}
			//结束panduan
			for(int i=1;i<lenth;i++)
			{
				if(snakeX[0]==snakeX[i] && snakeY[0]==snakeY[i])
					isFail = true;
			}
			
			repaint();
		}
		timer.start();//让时间动起来
	}
	

	
}

StartGames.java

package snake;

import javax.swing.*;

public class StartGames {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		//绘制一个静态窗口 JFrame
		JFrame frame = new JFrame("贪吃蛇");
		frame.setBounds(10,10,900,720);//设置界面大小
		frame.setResizable(false);
		frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//让游戏能够关闭
		//面板Jpanel 可以加入到JFrame
		frame.add(new GamePanel());
		
		frame.setVisible(true);//让窗口可以显示出来
	}

}

代码好了，接下来是静态资源:
body

header

left

right

up

food

down

学习的视频链接