用JAVA获取文件的MD5哈希码

获取文件的哈希码是一项常见的编程任务。MD5 是一种非常流行和常用的哈希算法。使用 Java 可以轻松获取文件的 MD5 哈希码，如下面的代码所示：

import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.security.MessageDigest;public class MD5file {public static String md5OfFile(File file) throws Exception {MessageDigest md = MessageDigest.getInstance("MD5");FileInputStream fs = new FileInputStream(file);BufferedInputStream bs = new BufferedInputStream(fs);byte[] buffer = new byte[1024];int bytesRead;while ((bytesRead = bs.read(buffer, 0, buffer.length)) != -1) {md.update(buffer, 0, bytesRead);}byte[] digest = md.digest();StringBuilder sb = new StringBuilder();for (byte bite : digest) {sb.append(String.format("%02x", bite & 0xff));}return sb.toString();}public static void main(String[] args) {File md5file = new File("f:\\Fedora-KDE-Live-x86_64-34-1.2.iso");try {String out = md5OfFile(md5file);System.out.println(out);} catch (Exception e) {// TODO Auto-generated catch blocke.printStackTrace();}}}

上面的代码做了几件事：

• 创建一个MessageDigest最终会创建 MD5 哈希码的对象
• 使用FileInputStream和BufferedInputStream缓冲来自文件的输入
• 每读取 1024 个字节更新MessageDigest对象update()
• 使用digest()方法返回文件的MD5哈希码
• 将此 MD5 哈希码转换为十六进制格式

import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException;public class MD5file2 {public static void main(String[] args) throws NoSuchAlgorithmException, IOException {File file = new File("f:\\Fedora-KDE-Live-x86_64-34-1.2.iso");MessageDigest md = MessageDigest.getInstance("MD5");FileInputStream fs = new FileInputStream(file);BufferedInputStream bs = new BufferedInputStream(fs);byte[] buffer = new byte[1024];int bytesRead;while ((bytesRead = bs.read(buffer, 0, buffer.length)) != -1) {md.update(buffer, 0, bytesRead);}byte[] digest = md.digest();StringBuilder sb = new StringBuilder();for (byte bite : digest) {sb.append(String.format("%02x", bite & 0xff));}System.out.println(sb.toString());}} import java.io.BufferedInputStream; import java.io.File; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException;public class MD5file3 {public static void main(String[] args) {File file = new File("f:\\Fedora-KDE-Live-x86_64-34-1.2.iso");MessageDigest md = null;try {md = MessageDigest.getInstance("MD5");} catch (NoSuchAlgorithmException e) {// TODO Auto-generated catch blocke.printStackTrace();}FileInputStream fs = null;try {fs = new FileInputStream(file);} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}BufferedInputStream bs = new BufferedInputStream(fs);byte[] buffer = new byte[1024];int bytesRead;try {while ((bytesRead = bs.read(buffer, 0, buffer.length)) != -1) {md.update(buffer, 0, bytesRead);}} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}byte[] digest = md.digest();StringBuilder sb = new StringBuilder();for (byte bite : digest) {sb.append(String.format("%02x", bite & 0xff));}System.out.println(sb.toString());}}

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