java下载文件时如何验证文件完整性

?Java???????????????????????????????????????,??????????????,????????????????????MD5?SHA-1?SHA-256??

?????????,?????Java???MD5????????????:

import java.io.File;
import java.io.FileInputStream;
import java.security.MessageDigest;

public class FileIntegrityChecker {

    public static String calculateMD5(File file) {
        try {
            MessageDigest md = MessageDigest.getInstance("MD5");
            FileInputStream fis = new FileInputStream(file);
            byte[] buffer = new byte[8192];
            int bytesRead;
            while ((bytesRead = fis.read(buffer)) != -1) {
                md.update(buffer, 0, bytesRead);
            }
            fis.close();
            byte[] md5sum = md.digest();
            StringBuilder sb = new StringBuilder();
            for (byte b : md5sum) {
                sb.append(String.format("x", b));
            }
            return sb.toString();
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static void main(String[] args) {
        File file = new File("test.txt");
        String expectedMD5 = "e5398e26e6e735a6f56ecf4d9d1b3a8c";
        String actualMD5 = calculateMD5(file);
        if (expectedMD5.equals(actualMD5)) {
            System.out.println("File integrity verified.");
        } else {
            System.out.println("File integrity verification failed.");
        }
    }
}

???????,???????calculateMD5??,???????File??????,?????MD5????????16???????????main???,??????test.txt???????MD5???,????MD5???????,??????????

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