我做了一个在键盘上移动玩家的游戏，通过随机吃硬币来增加分数。当你触摸tnt时，hp降低，当你触摸咖啡时，hp升高。使用图形g在屏幕上打印。现在我要添加一个计时器。我想做一个游戏，让玩家在规定的时间内取得高分。有很多事情我还不知道。请给我建议，这是我的密码。谢谢你看。

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;
import java.io.File;
import java.io.IOException;

import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.LineUnavailableException;
import javax.sound.sampled.UnsupportedAudioFileException;
import javax.swing.ImageIcon;
import javax.swing.JFrame;

public class CoinEat1 extends JFrame {
   private Image bufferImage;
   private Graphics screenGraphic; 

   private Clip clip;

   private Image backgroundImage = new ImageIcon("src/images/배경.jpg").getImage();
   private Image player = new ImageIcon("src/images/1P.png").getImage();
   private Image coin = new ImageIcon("src/images/코인.png").getImage();
   private Image TNT = new ImageIcon("src/images/폭탄.png").getImage();
   private Image Coffee = new ImageIcon("src/images/커피.png").getImage();

   private int playerX,playerY;
   private int playerWidth = player.getWidth(null); 
   private int playerHeight = player.getHeight(null); 

   private int coinX,coinY;
   private int coinWidth = coin.getWidth(null);
   private int coinHeight = coin.getHeight(null);

   private int TNTX,TNTY;
   private int TNTWidth = TNT.getWidth(null);
   private int TNTHeight = TNT.getHeight(null);

   private int CoffeeX,CoffeeY;
   private int CoffeeWidth = Coffee.getWidth(null);
   private int CoffeeHeight = Coffee.getHeight(null);

   private int score;

   private int HP;

   private boolean playerup, down, left, right; 

   public CoinEat1() {
      setTitle("동전JAVA");
      setVisible(true);
  setSize(Main.SCREEN_WIDTH,Main.SCREEN_HEIGHT);
  setLocationRelativeTo(null);
  setResizable(false);
  setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

  addKeyListener(new KeyAdapter(){
     public void keyPressed(KeyEvent e) { 
        switch(e.getKeyCode()) {
        case KeyEvent.VK_UP:
           playerup=true;
           break;
        case KeyEvent.VK_DOWN:
           down=true;
           break;
        case KeyEvent.VK_LEFT:
           left=true;
           break;
        case KeyEvent.VK_RIGHT:
           right=true;
           break;   
        }
     }

     public void keyReleased(KeyEvent e) { 
        switch(e.getKeyCode()) {
        case KeyEvent.VK_UP:
           playerup=false;
           break;
        case KeyEvent.VK_DOWN:
           down=false;
           break;
        case KeyEvent.VK_LEFT:
           left=false;
           break;
        case KeyEvent.VK_RIGHT:
           right=false;
           break;   
        }
     }      
  });

  Init();

  while(true){
     try {
        Thread.sleep(20);
     } catch(InterruptedException e) {
        e.printStackTrace();
     }
     keyProcess();
     CoinCrashCheck();
     TNTCrashCheck();
     CoffeeCrashCheck();
  }
   }

   public void Init() {
      score = 0;

  HP = 100;

  playerX = (Main.SCREEN_WIDTH-playerWidth)/2; 
  playerY = (Main.SCREEN_HEIGHT-playerHeight)/2;

  coinX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth));
  coinY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerHeight-30))+30;

  TNTX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth)); 
  TNTY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerHeight-30))+30;

  CoffeeX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth)); 
  CoffeeY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerWidth))+30;

      playsound("src/music/BGM.wav",true);
   }

   public void keyProcess() {
      if (playerup && playerY - 3 > 30) playerY-=3;
      if (down && playerY + playerHeight + 3 < Main.SCREEN_HEIGHT) playerY+=3;
      if (left && playerX -3 > 0) playerX-=3;
      if (right && playerX + playerWidth + 3 < Main.SCREEN_WIDTH) playerX+=3;
   }

   public void CoinCrashCheck(){
      if (playerX+playerWidth > coinX && coinX+coinWidth > playerX && playerY+playerHeight > coinY && coinY+coinHeight > playerY){ 
         score += 100;
         playsound("src/music/coin.wav",false);
         coinX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth));
         coinY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerHeight-30))+30; 
      }
   }

   public void TNTCrashCheck() { 
        if (playerX+playerWidth > TNTX && TNTX+TNTWidth > playerX && playerY+playerHeight > TNTY && TNTY+TNTHeight > playerY){ 
        HP -= 25;
        TNTX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth));
        TNTY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerHeight-30))+30; 
        }
    }

   public void CoffeeCrashCheck() { 
        if (playerX+playerWidth > CoffeeX && CoffeeX+CoffeeWidth > playerX && playerY+playerHeight > CoffeeY && CoffeeY+CoffeeHeight > playerY){ 
            HP += 25; 
            CoffeeX = (int)(Math.random()*(Main.SCREEN_WIDTH+1-playerWidth));
            CoffeeY = (int)(Math.random()*(Main.SCREEN_HEIGHT+1-playerHeight-30))+30; 
            }
    }

   public void playsound(String pathName, boolean isLoop) {
        try {
            clip = AudioSystem.getClip();
            File audioFile = new File(pathName);
            AudioInputStream audioStream = AudioSystem.getAudioInputStream(audioFile);
            clip.open(audioStream);
            clip.start();
            if(isLoop) 
                clip.loop(Clip.LOOP_CONTINUOUSLY);
        }catch (LineUnavailableException e) {
            e.printStackTrace();
        }
        catch (UnsupportedAudioFileException e) {
            e.printStackTrace();
        }
        catch (IOException e) {
            e.printStackTrace();
        }
    }

   public void paint(Graphics g) {
      bufferImage = createImage(Main.SCREEN_WIDTH,Main.SCREEN_HEIGHT); 
      screenGraphic = bufferImage.getGraphics();  
      screenDraw(screenGraphic);
      g.drawImage(bufferImage,0,0,null); 
   }

   public void screenDraw(Graphics g){//이미지를 출력해줄 paint 메소드
      g.drawImage(backgroundImage,0,0,null);
      g.drawImage(player,playerX,playerY,null);
      g.drawImage(coin,coinX,coinY,null);
      g.drawImage(TNT,TNTX,TNTY,null);
      g.drawImage(Coffee,CoffeeX,CoffeeY,null);

      g.setColor(Color.white);
      g.setFont(new Font("Arial",Font.BOLD,35));
      g.drawString("SCORE : "+score, 30, 80);
      g.drawString("HP : " + HP, 30, 120);

      this.repaint(); 
   }

   public static void main(String[] args) {
      new CoinEat1();

   }

}