Graphics2D 无法解析为类型

Question

我在按照教程创建游戏时遇到错误。它显示 Graphics2D 无法解析为类型。我是 java 的新手，我正在使用 Eclipse IDE (JavaSE-12)。我导入了 import java.awt.Graphics2D，它似乎消除了错误，但只要我运行程序，错误就会再次出现。其他一切正常，让我导入其他东西（例如图形、维度和 JPanel）。我会很感激你的回答！

package main;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;

import javax.swing.JPanel;

public class GamePanel extends JPanel implements Runnable{
    
    //screen settings
    final int originalTileSize = 16;
    final int scale = 3; // 48x48

    final int tileSize = originalTileSize * scale;
    final int maxScreenCol = 16;
    final int maxScreenRow = 12;
    final int screenWidth = tileSize * maxScreenCol;
    final int screenHeight = tileSize * maxScreenRow;
    
    Thread gameThread;
    
    public GamePanel() {
        
        this.setPreferredSize(new Dimension(screenWidth, screenHeight));
        this.setBackground(Color.pink);
        this.setDoubleBuffered(true);
    }

    public void startGameThread() {
        
        gameThread = new Thread(this);
        gameThread.start();
    }
    
    @Override
    public void run() {

        while(gameThread != null) {
            update();
            
            repaint();
        }
        
    }
    
    public void update() {
        
    }
    
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        Graphics2D g2 = (Graphics2D)g; <--- this line shows an error
        
        // (I'm trying to create a rectangle after I resolve the issue with Graphics)
        //g2.setColor(Color.white);
        //g2.fillRect(100, 100, tileSize, tileSize);
        //g2.dispose();
    }
}