MessageDigest类封装得很不错，简单易用
不多说，直接上代码
import java.io.FileInputStream;
import java.security.MessageDigest;
import java.util.Scanner;
public class MD5Test {
public static void main(String[] args) {
System.out.print("输入文件名：");
Scanner inputFromConsole = new Scanner(System.in);
String filename = inputFromConsole.nextLine();
try (FileInputStream inputFromFile = new FileInputStream(filename)) {
MessageDigest md5 = MessageDigest.getInstance("MD5");
byte[] buffer = new byte[10 * 1024 * 1024];
int byteCount;
while ((byteCount = inputFromFile.read(buffer)) != -1) {
md5.update(buffer, 0, byteCount);
}
StringBuilder result = new StringBuilder();
byte[] digested = md5.digest();
for (byte e : digested) {
String hexStr = Integer.toHexString(e & 255);
if (hexStr.length() == 1)
result.append('0');
result.append(hexStr);
}
System.out.println(result);
} catch (Exception ex) {
ex.printStackTrace();
}
}
}