Sample Code to Get MD5 Checksum of a File in Android

When downloading a file over internet, the uploader usually provides an MD5 checksum for the file to ensure the integrity of the file. MD5 checksum (message digest) is something like a fingerprint or digital signature for  a file. The checksum is unique for a file and  there is very small possibility of getting two identical checksums for two different files. In Android, using java security package we can compute the md5 message digest for a file. Here is a sample class to get MD5 checksum from an input stream:

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package net.londatiga.android.util;   import java.security.MessageDigest;   import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream;   public class Util {     private static char[] hexDigits = "0123456789abcdef".toCharArray();       public static String md5(InputStream is) throws IOException {         String md5 = "";           try {             byte[] bytes = new byte[4096];             int read = 0;             MessageDigest digest = MessageDigest.getInstance("MD5");               while ((read = is.read(bytes)) != -1) {                 digest.update(bytes, 0, read);             }               byte[] messageDigest = digest.digest();               StringBuilder sb = new StringBuilder(32);               for (byte b : messageDigest) {                 sb.append(hexDigits[(b >> 4) & 0x0f]);                 sb.append(hexDigits[b & 0x0f]);             }               md5 = sb.toString();         } catch (Exception e) {             e.printStackTrace();         }           return md5;     } }

To get md5 checksum from a file and compare it with original md5:

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try {       String md5Origin  = "";//original file's md5 checksum       String filePath   = ""; //fill with the real file path name         FileInputStream fis   = new FileInputStream(filePath);       String md5Checksum    = Util.md5(fis);         if (md5Checksum.equals(md5Origin)) {           //file is valid       } } catch (Exception e) { }