在Java中，可以使用URL和HttpURLConnection類來下載圖片。以下是一個簡單的示例代碼：

import java.io.BufferedInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;

public class ImageDownloader {
    public static void main(String[] args) {
        String imageUrl = "http://example.com/image.jpg";
        String destinationPath = "C:/path/to/save/image.jpg";
        
        try {
            URL url = new URL(imageUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            
            InputStream inputStream = connection.getInputStream();
            BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
            
            FileOutputStream fileOutputStream = new FileOutputStream(destinationPath);
            
            byte[] buffer = new byte[1024];
            int bytesRead;
            while ((bytesRead = bufferedInputStream.read(buffer)) != -1) {
                fileOutputStream.write(buffer, 0, bytesRead);
            }
            
            fileOutputStream.close();
            bufferedInputStream.close();
            
            System.out.println("Image downloaded successfully.");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

只需將imageUrl替換為要下載的圖片的URL，將destinationPath替換為要保存圖片的路徑，運行代碼即可下載圖片。