工具类代码

package com.example.util;

import org.apache.commons.io.FileUtils;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;


/**
 * 文件相关工具类
 */
public class FileUtil {
    /**
     * 获取网络文件的大小
     * @param fileUrl
     * @return
     */
    public static int getFileSize(String fileUrl) {

        if (fileUrl == null || "".equals(fileUrl)) {
            return 0;
        }

        int fileSize = 0;

        URL url = null;
        URLConnection conn = null;

        try {
            url = new URL(fileUrl);
        } catch (MalformedURLException e) {
            e.printStackTrace();
        }

        if (url != null) {
            try {
                conn = url.openConnection();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

        if (conn != null) {
            fileSize = conn.getContentLength();
        }

        return fileSize;
    }
}

测试示例

package com.example.util;

import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.*;

class FileUtilTest {

    @Test
    void getFileSize() {
        String fileUrl = "https://pdf.dfcfw.com/pdf/H3_AP202402221622830899_1.pdf?1708673604000.pdf";
        int fileSize = FileUtil.getFileSize(fileUrl);
        System.out.println(fileSize); // 435324 == 425 KB
    }
}